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GENERAL  OFFICE  OF  THE  WESTERN  UNION  TELEGRAPH   COMPANY,  CORNER 
BROADWAY  AND  LIBERTY  STREET,  NEW  YORK. 


^MODERN  PRACTICE 

or  THE 

ELECTRIC  TELEGRAPH. 

.X 

A  HANDBOOK 

TOB 

ELECTRICIANS  AND  OPERATORS. 


BY  FRANK  L.  POPE. 


SIXTH     EDITION. 

REVISED    AND    ENLARGED. 


D.   VAN    NOSTRAND,    Publisher, 

23  MTTBBAY  STBEET  &  27  WABBEX  STBEBT. 
1872. 


Entered  according  to  act  of  Congress,  in  the  year  1372,  by 

D.  VAN  NOSTRAND, 
In  the  Office  of  the  Librarian  of  Congress,  at  Washington. 


-rx 


PREFACE  TO  THE  FOURTH  EDITION. 


During  the  quarter  of  a  century  which  has  elapsed  since  the 
introduction  of  the  Electric  Telegraph  in  the  United  States,  thosd 
engaged  in  its  service  have  been  almost  entirely  dependent  upon 
verbal  instruction,  and  long  practical  experience,  for  a  thorough 
technical  knowledge  of  their  profession.  The  works  accessible 
to  the  American  telegrapher  have  been  of  a  popular,  rather  than 
of  a  strictly  scientific  character,  or  else  of  so  elementary  a  nature 
as  to  be  of  little  service  except  to  the  most  inexperienced  stu- 
dents. It  is  true  that  a  number  of  excellent  foreign  works  have 
appeared  within  a  few  years  ;  yet  the  difficulty  and  expense  of 
obtaining  them,  as  well  as  their  want  of  applicability  to  the 
American  telegraphic  system,  has  prevented  their  general  circu- 
lation among  the  class  for  which  this  work  is  more  especially 
designed. 

The  unexpectedly  favorable  reception  which  has  been  accorded 
to  the  first  three  editions  of  this  work,  has  led  the  author  to 
believe  that  it  has,  to  some  extent,  supplied  the  acknowledged 
deficiency  which  had  previously  existed  in  this  branch  of  litera- 
ture. The  present  edition  has  been  carefully  revised,  as  well  as 
enlarged  by  the  addition  of  much  new  matter,  and  is  believed  to 
embrace  all  the  recent  discoveries  and  improvements  in  practical 
telegraphy,  which  have  successfully  passed  through  the  test  of 
actual  experience. 

The  methods  of  testing  telegraph  lines  and  apparatus  by  actual 
measurement,  which  are  now  universally  employed  in  Europe, 
and  to  some  extent  in  this  country,  have  been  treated  upon  to 
an  extent  commensurate  with  the  importance  of  the  subject.  It 
is  hoped  that,  with  the  aid  of  this  work,  the  student  may  obtain 
a  complete  and  satisfactory  knowledge  of  this  useful  and  beauti- 
ful system. 

The  principles  laid  down  for  the  guidance  of  the  student  in 
the  formation  of  the  telegraphic  alphabet,  and  the  subsequent 


IV  PREFACE. 

progressive  exercises  intended  for  practice  with  the  key,  differ 
but  slightly  from  those  employed  by  the  author,  while  teaching 
a  class  of  students  for  the  American  Telegraph  Company  in  1864. 
This  plan  was  believed  at  that  time  to  be  original,  but  as  a  method 
of  teaching,  involving  substantially  the  same  principles,  was 
devised  and  subsequently  published  by  Prof.  J.  E.  Smith,  in  his 
Manual  of  Telegraphy,  it  seems  proper  to  make  this  explanation 
of  the  circumstances. 

Among  the  additional  matter  in  the  present  edition  will  be 
found  an  entire  new  chapter  upon  the  Eecent  Improvements  in 
Telegraphic  Practice,  as  well  as  a  number  of  articles  in  the 
Appendix,  on  the  Equipment  of  Telegraph  Lines,  the  Working 
Capacity  of  Telegraph  Lines,  and  the  Electrical  Tension  of  Bat- 
teries and  Lines,  etc.,  etc. 

Most  of  the  illustrations  in  this  volume  have  been  engraved 
expressly  for  its  pages,  from  original  drawings  by  the  author. 

In  conclusion,  the  author  desires  to  express  his  acknowledg- 
ments to  his  friend  David  Brooks,  for  much  valuable  aid  in  the 
preparation  of  this  work,  especially  of  the  present  edition  ;  and 
he  would  likewise  take  occasion  to  thank  Mr.  G.  Farmer,  for 
information  which  has  been  kindly  supplied  by  him.  Much 
useful  material  has  also  been  obtained  from  Sabine's  Electric 
Telegraph,  Culley's  Hand-Book  of  the  Electric  Telegraph,  Clark's 
Electrical  Measurement,  Varley's  Report  on  the  Condition  of  the 
Western  Union  Lines,  and  the  columns  of  The  Telegrapher. 

ELIZABETH,  N.  J.,  January,  1871. 


CONTENTS. 

CHAPTER    I 

ORIGIN  OF   THE   ELECTRIC   CURRENT. — GALVANIC   BATTERIES. 

MM. 

Simple  Galvanic  Circuit 9 

Conductors  and  Non- Conductors 10 

Electrical  Tension 11 

Electrical  Quantity 11 

The  Daniell  Battery 12 

Effect  of  Continued  Action 13 

The  Deposit  of  Copper  upon  the  Porous  Cup It 

Renewal  of  the  Battery H 

Application  of  the  Darnell  Battery  to  Main  Circuits 13 

The  Grove  Battery 15 

Setting  up  a  Grove  Battery 16 

The  Carbon  Battery 17 

Power  of  the  Carbon  Battery 19 

Insulation  of  Batteries 20 

CHAPTER    II. 

ELECTRO-MAGNETISM. 

Deflection  of  the  Magnetic  Needle 21 

Electro-Magnets 22 

Intensity  and  Quantity  Magnet 22 


CHAPTER    III. 

TELEGRAPHIC   CIRCUITS. 

Resistance  of  the  Circuit 24 

Electrical  Measurement 25 

Resistance  Coils 25 

Simple  Telegraphic  Circuit 25 

The  Earth  Circuit 26 

Arrangement  of  the  Batteries 26 

Intermediate  Stations 28 


VI 


CONTEXTS. 


The  Morse  System 26 

Other  Telegraphic  Systems 27 


CHAPTER    IV. 

THE  MORSE,   OB  AMERICAN   TELEGRAPHIC  SYSTEM. 

The  Morse  Signal  Key 28 

The  Morse  Register 29 

The  Relay  Magnet 30 

The  Sounder 32 

Arrangement  of  a  Terminal  Station 34 

Arrangement  of  a  "Way  Station , 35 

Adjustment  of  the  Apparatus 3G 

SWITCHES  OR  COMMUTATORS 37 

The  Plug  Switch 39 

The  Universal  Switch 39 

Arrangement  of  the  Connections 41 

Jones'  Lock  Switch 41 

Lightning  Arresters. 42 

The  Plate  Arrester 43 

Bradley's  Arrester 43 

REPEATERS 45 

"Wood's  Button  Repeater • 46 

Hicks'  Automatic  Repeater 47 

Milliken's  Repeater. 50 

Bunnell's  Repeater 52 

Combination  Locals 55 

Local  Circuit  Changer 56 

Technical  Terms  used  in  the  Telegraph  Service 57 


CHAPTER    V. 

INSULATION. 

The  Glass  Insulator 59 

The  "Wade  Insulator 60 

The  Hard  Rubber  Insulator. 60 

The  Leflerts  Insulator 61 

The  Brooks  Insulator 61 

Brooks'  Stone-ware  Insulator 62 

Mode  of  Testing  Insulators 62 

Escape 63 

"Weather  Cross 63 

Effect  of  Escapes  and  Grounds  upon  the  Circuit 63 

The  Laws  of  the  Electric  Current 64 

Practical  Application  of  Ohm's  Law 65 


CONTENTS.  YJ£ 

PAOB. 

Distribution  of  Batter7  Power 70 

Working  Several  Lines  from  One  Battery 71 


CHAPTER    VI. 

TESTING  TELEGRAPH  LIKES. 

Interruptions  to  which  Telegraph  Lines  are  Liable 73 

Testing  for  Disconnection 74 

Partial  Disconnection 75 

To  Test  for  an  Escape 75 

Testing  for  Grounds 76 

Testing  for  Crosses 76 

Testing  with  the  Galvanometer  and  Resistance  Coils. 78 

Testing  for  the  Distance  of  Faults 80 

The  Loop  Test 81 

Blavier's  Formula  for  Locating  an  Escape 84 

To  Find  the  Distance  of  a  Cross. 85 

Advantages  of  Testing  by  Measurement 86 

Testing  for  Conductivity  Resistance 87 


CHAPTER    VII. 

NOTES  ON  TELEGRAPHIC   CONSTRUCTION. 

Poles 89 

"Wire 89 

Galvanized  Wire 90 

Arrangement  of  Wires  upon  the  Pole. 90 

Joints  or  Splices 90 

Fixing  the  Insulators 91 

Leading  Wires  into  Offices 92 

Fitting  up  Offices 93 

Ground  Connections 93 

Cables 93 

Making  Joints  in  Cables 94 


CHAPTER     VIII. 

HINTS  TO   LEARNERS. 

Formation  of  the  Morse  Alphabet 96 

Elementary  Principles  of  the  Alphabet 97 

Exercises  for  Practice  in  Sending 99 

The  Alphabet  and  Numerals 101 

Beading  by  Sound 102 


Vlll  CONTENTS. 

CHAPTER     IX. 

BECENT  IMPROVEMENTS  IN  TELEGBAPHIC  PBACTICE. 

The  American  Compound  Wire 104 

The  Gravity  Battery 106 

Siemens'  Universal  Galvanometer 108 

Pope  and  Edison's  Printing  Telegraph 112 

CHAPTER    X. 

APPENDIX  AND   NOTES. 

The  Equipment  of  Telegraph  Lines 116 

The  Working  Capacity  of  Telegraph  Lines 121 

The  Electrical  Tension  of  Telegraph  Batteries  and  Lines 1 24 

Double  Transmission 131 

Edison's  Button  Eepeater 134 

Bradley's  Tangent  Galvanometer 135 

Thompson's  Reflecting  Galvanometer 137 

Mode  of  Working  the  Atlantic  Cable 141 

Velocity  of  Electric  Signals 144 

Speed  of  Transmission 145 

Comparison  of  Wire  Gauges •  • 146 

Useful  Formula  for  Weight  and  Resistance  of  Wires 147 

Conducting  Powers  of  Materials 147 

Internal  Resistance  of  Batteries 149 

Electro-motive  Force  of  Different  Batteries 150 

Measurement  of  Electro-motive  Force 151 

Forces  of  Electro-magnets 151 

Electrical  Formulae 152 

Ohm's  Law 152 

Parallel  or  Derived  Circuits 153 

Galvanometers  and  Shunts 153 

Formula  for  the  Loop  Test 153 

Blavier's  Formula  for  Locating  a  Fault 154 

Measures  of  Resistance 154 

Strain  of  Suspended  Wires 154 

Index 157 


MODERN  PEACTICE 


or  THS 


ELECTRIC    TELEGRAPH. 

CHAPTER  I. 

ORIGIN  OP  THE  ELECTRIC  CURRENT. GALVANIC  BATTERIES. 


1.  SIMPLE  GALVANIC  CIRCUIT. — If  two  plates  of  dif- 
ferent metals,  such  as  copper  and  zinc  for  example,  are 
immersed  in  a  vessel  of  water  to  which  a  small  portion 
of  sulphuric  acid  has  been  added,  and  the  upper  ends  of 
the  two  plates  are  brought  in  contact,  or  connected 
together  with  a  metallic  wire  as  in  fig.  1,  a,  continuous 


current  of  electricity  will  pass  from  the  copper  to  the 
zinc  through  the  connecting  wire,  and  from  the  zinc  to 
the  copper  through  the  liquid,  as  indicated  by  the 
arrows  in  the  figure.  If  the  metallic  communication  be 
interrupted,  or  the  circuit,  as  it  is  termed,  broken,  the 
current  at  once  ceases,  but  is  instantly  renewed  when- 
ever the  connection  is  again  formed.  Electricity  pro- 
duced by  this  means  is  usually  termed  Galvanic  or  Vol- 
taic electricity,  from  the  names  of  its  discoverers,  and 
is  the  effect  of  chemical  action  by  the  acidulated  water 
upon  the  zinc. 


I  0  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

2.  The  plate  (usually  of  zinc),  upon  the  surface  of 
Which  the  electricity  is  generated  by  chemical  action,  is 
called  the  negative  pole,  and  the  opposite  plate,  gen- 
erally of  copper,  platina  or  carbon,  is  called  the  posi- 
tive pole.     They  are  also  frequently  designated  by  the 
signs  —  (minus)  and  +  (plus). 

3.  If  both  metals  in  this  arrangement  were  equally 
acted  upon  by  the  solution,  no  electricity  would  be  pro- 
duced, as  this  effect  arises  in  all  cases  from  the  differ- 
ence in  the  chemical  action  upon  the  two  plates.     For 
this  reason  the  positive  plate  is  made  of  some  metal  or 
other  substance  upon  which  the  liquid  has  little  or  no 
effect. 

4.  The  apparatus  for  producing  voltaic  electricity, 
which  has  been  described  in  its  simplest  form,  is  called 
a  battery.    As  electricity  is  produced  under  any  circum- 
stances in  which  the  above  conditions  have  been  com- 
plied with,  there  are  various  methods  of  constructing 
a  battery.     The  forms  used  in  the  practical  operation 
of  the  telegraph  will  hereafter  be  described  in  detail. 

5.  CONDUCTORS   AND  NON-CONDUCTORS. — Some  sub- 
stances, such  as  metals,  possess  the  property  of  allow- 
ing electricity  to  diffuse  itself  freely  throughout  their 
whole  substance,  and  are  therefore  termed  conductors. 
Others,  such  as  glass,  hard  rubber,  and  dry  wood,  offer 
great  resistance  or  opposition  to  this  diffusion,  and  are 
called  non-conductors  or  insulators. 

6.  This  division  however  is  relative  and  not  abso- 
lute.    Few  if  any  bodies   are  perfect  insulators,  and 
even  metals,  the  most  perfect  of  all  conductors,  offer 
some  resistance  to  the  passage  of  electricity,  or  in  other 
words  insulate  slightly.     A  good  insulator,  therefore, 
is  simply  a  bad  conductor,  and  vice  versa. 

7.  In  the  following  list  each  substance  named  con- 
ducts better  than  that  which  precedes  it,  the  first  being 
the  best  insulator  and  the  last  the  best  conductor  : 

1.  Dry  Air,  5.  India  Rubber,  9.  Silk, 

2.  Paraffine,  6.  Gutta  Percha,  10.  Dry  Paper, 

3.  Hard  Rubber,  7.  Sulphur,  11.  Porcelain, 
*.  Shellac,  8.  Glass,  12.  Dry  Wood, 


GALVANIC    BATTERIES.  11 

13.  Dry  Ice,  18.  Mercury,  23.  Zinc, 

14.  Water,  19.  Lead,  24.  Gold, 

15.  Saline  Solutions,  20.  Tin,  25.  Copper, 

16.  Acids,  21.  Iron,  26.  Silver. 

17.  Charcoal  or  Coke,  22.  Platinum, 

8.  ELECTRICAL  TENSION. — If  two  or  more  simple  bat- 
teries, or  elements  as  they  are  called,  are  connected  to- 
gether in  such  a  manner  that  the  positive  plate  of  the 
lirst  is  united  by  a  metallic  conductor  with  the  negative 
plate  of  the  second,  and  so  on,  as  shown  in  fig.  2,  the 


electrical  tension,  or  power  of  overcoming  resistance,  is 
increased  in  direct  proportion  to  the  number  of  ele- 
ments. Four  elements  will  therefore  possess  four  times 
the  tension  of  one  element,  and  the  current  generated 
by  their  combined  action  will  be  capable  of  overcoming 
four  times  the  resistance  of  that  from  a  single  element. 
9.  ELECTRICAL  QUANTITY. — It  is  important,  however, 
to  observe,  that  although  the  tension  increases  with 
each  element  added  to  the  series,  no  greater  quantity  is 
produced  by  a  great  number  of  elements  than  by  a 
single  one — the  action  in  each  cell  serving  only,  as  it 
were,  to  urge  forward  a  quantity  equal  to  that  arising 
from  chemical  decomposition  in  the  first  cell.  If,  on  the 
contrary,  we  connect  together  the  four  zincs  and  the 
four  coppers,  forming  in  effect  a  single  element,  with 
plates  equivalent  to  four  times  the  original  surface, 
there  will  be  four  times  the  original  quantity  of  electri- 
city generated  ;  but  its  tension,  or  power  of  overcom- 
ing resistance,  will  be  no  greater  than  that  of  a  single 
pair  of  plates.  This  distinction  is  of  great  importance, 


12 


MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 


and  should  be  thoroughly  understood  and  carefully  re- 
membered. 

10.  In  the  simple  form  of  battery  previously  described 
(8),  if  the  poles  are  united  by  a  conductor  for  a  consider- 
able length  of  time,  bubbles  of  hydrogen,  arising  from 
the  decomposition  of  the  water,  cover  the  positive  plate, 
and  in  a  great  measure  prevent  the  liquid  from  coming 
in  contact  with  it,  and  the  surface  of  the  plate  also  be- 
comes coated  with  a  deposit  of  zinc,  tending  to  convert 
the  battery  into  one  in  which  both  plates  are  of  zinc, 
and  thus  its  electro-motive  force  is  weakened  and  finally 
destroyed.  In  order  to  render  the  battery  constant  in 
its  action,  it  is  necessary  to  prevent  these  effects  by 
surrounding  the  negative  plate  with  a  solution  of  a  salt 
of  the  metal  itself.  This  principle  is  employed  in  the 
arrangement  about  to  be  described. 


11.  THE  DANIELL  BATTERY.— This  combination  con- 
sists of  a  jar  of  glass  or  earthenware,  F  (fig.  3),  about  six 


GALVANIC    BATTERIES. 


inches  in  diameter  and  eight  or  nine  inches  high.  A 
plate  of  copper,  G,  is  bent  into  a  cylindrical  form,  so  as 
to  fit  within  it,  and  is  provided  with  a  perforated  cham- 
ber, to  contain  a  supply  of  sulphate  of  copper  in  crys- 
tals, and  a  strap  of  the  same  metal  with  a  clamp  for 
connecting  it  to  the  zinc  of  the  next  element.  H  is  a 
porous  cup,  as  it  is  technically  termed,  made  of  unglazed 
earthenware,  six  or  seven  inches  high  and  two  inches  in 
diameter,  within  which  is  placed  the  zinc,  X.  This  is 
usually  of  the  shape  shown  in  the  figure,  which  is  called 
the  "star  zinc,"  but  it  is  often  made  in  the  form  of  a 
hollow  cylinder,  the  latter  giving  greater  power,  but 
being  somewhat  more  difficult  to  clean. 

The  outer  cell  is  filled  with  a  saturated  solution  of 
sulphate  of  copper  (blue  vitriol),  and  the  porous  cell 
with  a  solution  of  sulphate  of  zinc.  A  series  of  three 
elements  connected  together,  as  usually  employed  on 
American  lines  for  a  local  battery,  is  shown  at  I. 

12.  EFFECT  OF   CONTINUED  ACTION.  —  By  continued 
action  sulphate  of  zinc  is  formed  in  the  porous  cup,  and 
the  sulphate  of  copper  in  the  outer  cell  consumed,  the  zinc 
being  constantly  dissolved  away  while  the  copper  plate 
is  at  the  same  time  increased.     When  all  the  sulphate 
of  copper  has  been  decomposed,  and  the  water  in  the 
zinc  compartment  saturated  with  sulphate  of  zinc,  the 
action  of  the  battery  ceases.     Some  of  the  sulphate  of 
zinc  in  this  case  usually  passes  into  the  copper  cell,  and 
appears  upon  the  copper  plate  in  the  form  of  a  black 
powder  ;  it  is  therefore  necessary  to  maintain  a  con- 
stant supply  of  pulverized  vitriol  in   the   perforated 
chamber  attached  to  the  copper  cylinder. 

13.  When  the  solution  in  the  porous  cup  becomes  satu- 
rated with  sulphate  of  zinc  it  crystallizes  upon  the  zinc 
plate,  interfering  with  the  action  of  the  battery.     Part 
of  this  solution  should  therefore  be  removed  occasion- 
ally and  replaced  with  water. 

In  setting  up  the  battery  pure  water  may  be  used  in 
the  porous  cell,  and  the  battery  allowed  to  stand  a  few 
hours  with  a  closed  circuit,  when  it  will  be  found 


14  MODERN  PRACTICE  OF  THE  ELECTRIC  TEIEGRAPH. 

ready  for  use.     The  addition  of  a  little  sulphate  of  zinc 
will  greatly  hasten  its  action. 

14.  THE  DEPOSIT  OF  COPPER  UPON  THE  POROUS  CUP.— 
This  cannot  be  entirely  prevented,  but  may  be  greatly 
lessened  by  suspending  the  zinc  so  that  it  will  not  touch 
the  porous  cup  below  the  surface  of  the  liquid,  and  by 
saturating  the  bottom  of  the  cell  to  the  height  of  half 
an  inch  with  melted  paraffine,  or  even  tallow. 

15.  When  constructed  as  above  described  and  used 
in  a  local  circuit,  the  Daniell  batter}--  will  continue  in 
action  about  ten  or  fifteen  days  without  attention,  the 
time  depending  upon  the  size  of  the  wire  in  the  magnet 
and  the  amount  of  daily  service.     The  sulphate  of  cop- 
per solution  should  be  kept  of  good  strength,  otherwise 
the  upper  portion  becomes  weak  and  an  extra  current 
is  set  up  within  the  battery,  which  tends  to  eat  away 
and  destroy  the  copper  plate  without  any  useful  effect. 

16.  RENEWAL  OP  THE  BATTERY. — In  renewing  this 
battery  the  zincs  should  be  scraped  and  well  cleaned 
with  a  stiff  brush,  the  porous  cups  thoroughly  washed, 
and  the  old  solution  contained  in  them  thrown  out,  with 
the  exception  of  about  one  third  of  the  clear  portion, 
which  should  be  returned,  otherwise  the  battery  will 
require  some  hours  to  recover  its  full  strength.     The 
copper  deposit  upon  the  zincs  is  valuable,  and  should  be 
preserved. 

Every  two  or  three  months  the  coppers  ought  to  be 
taken  out  and  the  deposit  upon  their  surface  removed, 
which  may  be  done  two  or  three  times.  When  they 
become  too  much  encrusted  to  afford  room  for  the  po- 
rous cups  they  must  be  replaced  by  new  ones. 

Porous  cups  ought  to  be  renewed  whenever  they  be- 
come too  much  encrusted  with  copper.  If  cracked  they 
should  be  changed  at  once,  otherwise  a  great  waste  of 
material  will  ensue. 

17.  The  crystals  which  form  around  the  edge  of  the 
outer  jar  require  to  be  occasionally  wiped  off  with  a 
damp  cloth,  or  they  will  eventually  run  down  the  out- 
side and  form  a  connection  between  the  jars,  giving  rise 


GALVANIC    BATTERIES. 


15 


to  a  great  consumption  of  material  without  correspond- 
ing benefit. 

18.  In  order  that  the  current  may  act  with  its  full 
force,  it  is  necessary  to  keep  the  clamps  and  connec- 
tions of  the  battery  clean  and  bright,  and  free  from  rust 
or  dirt.     As  chemical  action  is  promoted  by  heat,  the 
battery  will  act  more  vigorously  if  kept  in  a  warm 
place. 

19.  APPLICATION  OP  THE  DANIELL  BATTERY  TO  MAIN 
CIRCUITS. — This  battery  is  sometimes   used  for  main 
circuits,  but  in  that  case  it  is  preferable  to  arrange  it 
differently  by  placing  the  zincs  outside  and  the  copper 
within  the  porous  cell,  as  in  fig.  4,  in  which  Z  shows  the 


zinc  and  P  the  porous  cell.  The  copper,  C,  is  provided 
with  a  perforated  shelf,  D,  upon  which  the  vitriol  is 
placed. 

Other  forms  have  been  devised  which  dispense  en- 
tirely with  the  porous  cup,  the  two  solutions  being  sepa- 
rated by  the  difference  in  their  respective  specific  grav- 
ities. Some  of  these  bid  fair  to  come  into  extensive 
use. 

20.  THE  GROVE  BATTERY. — The  most  intense  and 
powerful  voltaic  combination  that  has  yet  been  dis- 
covered is  that  of  Grove.  For  many  years  it  was  ex- 
clusively used  for  telegraphic  purposes  in  this  country, 
and  is  still  employed  in  that  capacity  to  a  considerable 
extent.  Its  component  parts  are  shown  in  fig.  5,  in 
which  A  represents  a  glass  jar  or  tumbler,  about  3 


1  6  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 


inches  in  diameter  and  4£  inches  high.  A  thick  cylin- 
der of  zinc,  B,  of  a  size  nearly  sufficient  to  fill  the  tum- 
bler, is  placed  within  it,  and  is  furnished  with  a  project- 
ing arm,  to  which  is  attached  the  positive  plate  of  the 
next  element.  The  porous  cup,  C,  is  placed  within  the 
zinc.  A  thin  strip  of  platina,  D,  about  2<z  inches  long 
and  half  an  inch  in  width,  is  soldered  to  the  end  of  the 
zinc  arm  projecting  from  the  adjacent  cell,  and  reaches 
nearly  to  the  bottom  of  the  porous  cup. 

21.  SETTING  UP  A  GROVE  BATTERY. — It  is  necessary 
that  the  zinc  should  first  be  thoroughly  amalgamated. 
The  ordinary  zinc  of  commerce  contains  particles  of  lead, 
iron,  and  other  impurities,  which,  when  the  plate  is  im- 
mersed in  dilute  acid,  form  as  it  were  small  batteries 
upon  the  surface,  which  eat  away  numerous  cavities  in 
the  zinc  without  producing  any  useful  effect.  This  is 
termed  local  action,  and  may  be,  in  a  great  measure, 
prevented  by  the  above  process  of  amalgamation,  which 
is  usually  performed  by  immersing  the  zincs  in  a  vessel 
containing  dilute  muriatic  or  sulphuric  acid,  and  then 
plunging  them  in  a  bath  of  metallic  mercury.  After 
remaining  in  this  for  a  minute  or  two  they  are  taken 


GALVANIC    BATTERIES. 


17 


out  and  placed  in  a  vat  of  clean  water,  where  the  su- 
perfluous mercury  is  allowed  to  drain  off.  The  mercury 
dissolves  a  little  of  the  zinc,  which  flows  over  and  covers 
the  impurities,  and  prevents  the  acid  solution  from 
coming  in  contact  with  them. 

22.  In  putting  the  Grove  battery  together,  first  place 
the  glass  tumblers  in  position  and  fill  them  about  half 
full  of  a  solution  composed  of  one  part  of  sulphuric  acid 
and  twenty  to  thirty  parts  water,  by  measure,  thoroughly 
mixed.     Then   place   the   amalgamated   zincs   in   the 
tumblers,  with  the  arms  turned  at  right  angles  to  the 
line  of  cells.     Fill  the  porous  cups  nearly  full  of  strong 
nitric  acid  and  place  them  within  the  zincs,  then  turn 
the  zincs  around  so  as  to  immerse  the  platina  strips  in 
the  nitric  acid  of  the  adjoining  cell,  throughout   the 
whole  series,  as  shown  at  T,  in  tig.  5. 

23.  The  strength  of  the  dilute  sulphuric  acid  solu- 
tion in  this  battery  should  be  varied  in  proportion  to 
the  number  of  wires  worked  from  it.    The  less  the  num- 
ber of  the  latter  the  weaker  the  solution  may  be  made. 

24.  When  in  continuous  service  a  Grove    battery 
ought  to  be  taken  apart  every  night,  and  the  nitric  acid 
from  the  porous  cups  emptied  into  a  vessel  and  kept 
closed  until  morning.     The  zincs  should  be  removed 
and  placed  inverted  in  a  trough  of  water,  acidulated 
with  sulphuric  acid,  and  in  the  morning  rubbed  with  a 
brush,  and  the  mercury  diffused  evenly  over  their  sur- 
faces.    To  every  ten  parts  of  the  nitric  acid  taken  from 
the  battery  add  one  part  of  fresh  acid  every  morning. 
By  this  means  a  steady  and  uniform  current  will  be 
maintained  when  the  battery  is  in  action.     The  dilute 
sulphuric  acid  requires  renewal  about  twice  a  week.     In 
handling  this  battery  great  care  is  required  not  to  injure 
the  connection  between  the  zinc  and  the  platina.    A  set 
of  Grove  zincs,  in  continuous  service,  will  require  re- 
newal about  once  in  three  months. 

25.  THE  CARBON  BATTERY. — This  is  a  modification  of 
the  Grove  battery,  and  is  sometimes  called  the  Electrp- 
poion  battery.    It  is  extensively  employed  on  the  Ame- 


1  g  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

rican  lines  for  main  circuits.  In  its  general  construction 
and  arrangement  it  differs  but  little  from  the  battery 
last  described.  The  different  parts  of  which  it  is  com- 
posed are  shown  in  fig.  6,  consisting  of  a  glass  tum- 
bler, zinc  and  porous  cup.  In  place  of  the  platina  of 
the  Grove  battery,  a  plate  of  carbon  or  coke  is  em- 
ployed for  the  positive  element,  as  shown  in  the  figure. 


A  clamp  is  arranged  so  as  to  press  a  platina  button 
firmly  against  the  carbon,  this  button  being  permanently 
attached  to  a  wire  leading  to  a  binding  screw  on  the 
zinc  arm  of  the  next  element.  The  parts  are  usually 
made  of  about  the  same  size  as  in  the  Grove  battery. 

The  carbon  connection  is  sometimes  made  by  means 
of  a  platinized  copper  wire  inserted  into  its  upper  end, 
and  surrounded  with  lead,  to  prevent  the  action  of  the 
acids  upon  the  copper. 

26.  In  setting   up   this  battery  the  different  parts 


GALVANIC    BATTERIES.  ££ 

should  be  put  together  in  the  position  they  are  to  oc- 
cupy, as  shown  in  fig.  6,  and  care  taken  that  all  the  con- 
nections are  firmly  screwed  up.  The  zincs  must  be 
thoroughly  amalgamated,  and  the  dilute  sulphuric  acid 
solution  mixed  as  directed  for  the  Grove  battery.  A 
sufficient  quantity  of  this  solution  is  poured  into  the 
tumblers  to  cover  the  cj'lindrical  portion  of  the  zincs. 
The  porous  cups  are  then  filled  with  a  solution  of  bi- 
chromate of  potash,*  care  being  taken  not  to  pour  it 
upon  the  connections  or  clamps. 

27.  When  the  battery  is  in  service,  one  third  of  the 
bi-chromate  solution  in  the  porous  cups  should  be  re- 
moved every  morning  by  means  of  a  large  rubber  sy- 
ringe, and  replaced  with  fresh.    A  new  set  of  zincs  will 
require  to  be  amalgamated  a  second  time  after  having' 
been  in  use  three  or  four  days  ;  after  which  once  in  two 
to  four  weeks  will  be  often  enough — depending  some- 
what upon  the  amount  of  work  required  from  the  bat- 
tery.    The  battery  ought  to  be  taken  apart  every  two 
weeks,  the  zincs  brushed,  the  dilute  sulphuric  acid  solu- 
tion renewed,  and  the  carbons  thoroughly  soaked  in 
clean  water.     It  is  better,  if  possible,  to  have  a  spare 
set  of  cells  complete,  so  that  one  may  be  renewed  while 
the  other  is  in  use. 

28.  POWER  OF  THE  CARBON  BATTERY. — This  is  quite 
equal  to  that  of  the  Grove,  as  far  as  the  intensity  of  its 
action  is  concerned.     The   latter  however  will  work 
nearly  twice  as  many  wires  at  the  same  time  as  the 
former.     The  expense  of  the  carbon  battery  for  mate- 
rials and  attendance  is  less  than  one  third  that  of  the 
Grove.     A  set  of  zincs,  if  properly  cared  for,  will  last 
from  fourteen  to  sixteen  months  on  an  ordinary  tele- 
graph line.     It  is  a  good  plan  to  coat  the  zincs  with  as- 
phaltum  varnish  at  the  junction  of  the  projecting  arm, 
as  these  are  frequently  eaten  off  while  the  rest  of  the 
zinc  remains  in  good  condition. 

*  This  solution  is  made  as  follows  :  Mix  one  gallon  of  sulphuric  acid  and  three 
gallons  of  water.  Then,  in  a  separate  vessel,  dissolve  five  Ibs.  bi-chromate  of  pot- 
ash in  two  gallons  of  boiling  water  and  add  to  the  above,  mixing  the  whole  thor- 
oughly together.  The  proportion  of  bi-chromate  is  sometimes  made  one  fifth  greater 
than  the  amount  giveu. 


MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 


.  29.  INSULATION  OF  BATTERIES. — The  cells  of  a  bat- 
tery should  always  be  thoroughly  insulated  from  each 
other.     This  is  especially  important  in  the  case  of  the 
Grove  battery.     A   convenient  and 
effective  mode  of  insulation  is  shown 
in  fig.  7,  in  which  the  battery  tum- 
blers, AA,  are  set  upon  hollow  cy- 
linders of  wood,  BB,  saturated  with 
asphaltum  or  paraffine,  and  insulated 
from  the  upright  wooden  pins,  DD,  by 
the  glass  sockets,  CO.     The  pins  are 
FIG.  7.  inserted  into  a  horizontal  scantling, 

E,  which  forms  the  top  of  the  battery  stand. 
"  Battery  jars,  of  different  sizes,  are  now  made  at  the 
Brooks  Paraffine  Insulator  Works,  in  Philadelphia,  which 
are  composed  of  stone-ware,  thoroughly  saturated  with 
paraffine,  so  that  moisture  will  not  penetrate  them,  nor 
remain  upon  their  surface.  When  these  jars  are  em- 
ployed, no  special  insulation  is  required. 


CHAPTER  II. 


ELECTRO-MAGNETISM. 

30.  WHENEVER  the  poles  of  a  battery  are  connected 
by  a  conductor,  or  series  of  conductors,  so  as  to  form  a 
circuit,  a  current  of  electricity  is  assumed  to  flow  from 
the  negative  to  the  positive  pole,  through  the  battery 
itself,  and  from  the  positive  to  the  negative  pole  through 
the  conductor. 

31.  If  the  conducting  wire  is  covered  with  an  insu- 
lator (5),  such  as  silk  or  cotton,  so  as  to  compel  the 
current  to  traverse  its  entire  length,  and  is  wound  into  a 
spiral  or  coil,  surrounding  a  magnetic  needle,  the  needle 
will  be  deflected  from  its  natural  position,  and  will  tend 
to  take  up  a  position  at  right  angles  to  the  direction  of 
the  current.     If  the  current  be  passed  in  the  opposite 
direction  through  the  wire,  the  deflection  of  the  needle 
will  also  take  place  in  the  opposite  direction.    The  Gal- 
vanometer, an  extremely  useful  instrument  for  the  pur- 
pose of  indicating  the  presence,  direction,  and  strength" 
of  a  voltaic  current,  is  constructed  upon  this  principle. 

32.  If  the  conducting  wire,  covered  as  above,   be 
wound  upon  a  bar  of  soft  iron,  the  iron  becomes  mag- 
netic as  long  as  the  current  continues  to  flow,  and  pos- 
sesses the  property  of  attracting  other  pieces  of  iron  iii 
its   vicinity.     This  arrangement   is    called   an   electro- 
magnet. (34.) 

33.  If  the  iron  is  very  soft  and  pure  it  loses  its  mag- 
netism instantly  upon  the  cessation  of  the  current,  but 
if  impure,  or  if  hardened  by  hammering  or  turning,  it 
retains  a  certain  amount  of  residuary  magnetism,  espe- 
cially after  it  has  been  acted  upon  by  a  powerful  cur- 
rent.    It  is,  therefore,  necessary  that  the  iron  cores,  as 
they  are  termed,  of  electro-magnets,  should  be  annealed 
with  great  care. 


22  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

34.  ELECTRO-MAGXETS  are  generally  made  in  a  U 
form,  two  bobbins  or  spools,  a  a  (fig.  8),  being  filled 

with  covered  copper  wire,  and  the 
soft  iron  cores,  c  c,  passing  through 
them,  fixed  upon  a  connecting  bar, 
|«  b,  also  of  soft  iron,  as  shown  in  the 
figure.  The  two  spools,  a  and  a.  are 
virtually  continuations  of  one  spool, 
the  direction  being  apparently  re- 
versed by  the  bend  of  the  U-  The 
ends  of  the  cores,  c  c,  opposite  to  the  connecting  bar, 
are  called  the  poles  of  the  magnet,  the  magnetic  force 
being  accumulated  at  these  points.  The  bar  of  soft 
iron,  d,  upon  which  the  magnet  exerts  its  force,  is  called 
'the  armature. 

35.  In  electro-magnets  and  galvanometers  the  mag- 
netic effect  of  the  current  is  multiplied  by  the  number 
of  convolutions  of  the  wire  in  the  coil,  but  it  is  dimin- 
ished in  proportion  to  the  distance  of  the  wire  from  the 
core,  each  layer  of  wire  acting  with  less  power  than  the 
one  beneath  it. 

36.  Every  addition  to  the  length  of  the  conducting 
wire  enfeebles  the  current,  because  of  the  increased  re- 
sistance (5,  6,)  it  offers  to  its  passage.     In  a  very  long 
circuit,  such  as  a  telegraph  line,  the  action  of  the  cur- 
rent will  necessarily  be  feeble,  and  the  coil  is,  there- 
jfore,  made  of/we  wire,  which  occupies  little  space,  and 
allows  many  layers  to  be  wound  on  without  too  greatly 
increasing  the  distance  from  the  cores,  while  its  resist- 
ance is  too  small  in  proportion  to  the  rest  of  the  cir-r 
cuit  to  reduce  the  strength  of  the  current  materially. 

37.  When,  however,  the  circuit  is  very  short,  coarser 
wire  is  employed  in  the  coil.     A  fine  wire  would  add 
to  the  resistance  of  the  circuit  more  than  would  bq 
made  up  by  the  effect  of  an  increased  number  of  turns, 
for  even  a  very  few  layers  would  double  the  resistance 
pf  the  circuit. 

The  former  is  frequently  called  an  intensity,  and  the 
latter  a  quantity  magnet* 


ELECTRO-MAGNETISM.  .          23 

38.  Iron  docs  not  acquire  its  full  magnetism  instan- 
taneousl}',  and  the  act  of  demagnetization  also  requires 
time,  but  is  effected  more  rapidly  than  magnetization. 
The  greater  the  tension  of  the  battery  the  more  rapidly 
the  iron  acquires  its  magnetism  ;  therefore,  if  very 
rapid  action  is  required,  even  on  a  short  circuit,  a  num- 
ber of  cells  of  battery  must  be  used. 

It  has  also  been  ascertained  by  experiment  that  an 
electro-magnet  with  short  cores,  will  acquire  and  lose 
its  magnetism  with  much  greater  rapidity  than  one  with 
long  cores,  but  in  other  respects  similar. 


CHAPTER  III. 


TELEGRAPHIC    CIRCUITS. 

39.  A  TELEGRAPHIC  CIRCUIT  consists  of  one  or  more 
batteries,  the  line  wire,  the  instruments  and  the  earth. 
When  the  circuit  is  very  short  a  return  wire  is  fre- 
quently used  instead  of  the  earth. 

40.  Owing  to  the  immense  rapidity  with  which  the 
electric  force  is  propagated  throughout  a  circuit,  any 
effect  which  can  be  produced  at  hand  can  be  produced 
in  any  other  part  of  a  circuit,  however  distant,  at  the 
same  instant  of  time,  subject  to  a  diminution  of  force, 
arising  from  causes  which  diminish  the  quantity  of  elec- 
tricity, or  the  force  of  the  current  before  its  arrival  at 
the  distant  end,  thus  weakening  its  effect.     The  princi- 
pal causes  of  this  diminution  are  the  resistance  of  the 
circuit  and  defective  insulation,  in  consequence  of  which 
a  portion  of  the  current  escapes  from  the  line  to  the 
earth,  and  returns  without  traversing  the  distant  por- 
tion of  the  circuit. 

41.  The  effective  force  of  the  current  leaving  the  bat- 
tery depends  upon  two  things — the  tension  of  the  bat- 
tery, which  sets  the  current  in  circulation,  and  the 
resistance  the  current  encounters  in  traversing  the  cir- 
cuit. 

42.  RESISTANCE  OF  THE  CIRCUIT. — This  depends  upon 
the  length  and  size  of  the  conductor,  and  the  material 
of  which  it  is  composed.     In  an  ordinary  telegraphic 
line  wire  the  resistance  is  in  direct  proportion  to  its 
length,  arid  also  in  inverse  proportion  to  its  weight  per 
mile.     Thus,  150  miles  of  No.  8  wire  will  conduct  as 
well  as  100  miles  of  No.  10  wire,  and  as  great  an  effect 
can  be  produced  at  its  remote  end  with  a  battery  of 
equal  tension.     There  is,  therefore,  a  great  advantage 


TELEGRAPHIC     CIRCUITS.  25 

in  using  the  larger  sizes  of  wire  in  the  construction  of 
lines  intended  to  be  worked  in  long  circuits. 

43.  ELECTRICAL  MEASUREMENT. — In  order  to  institute 
a  comparison  between  the  resistances  of  different  cir- 
cuits, etc.,  a  standard  has  been  fixed  upon  by  the  Brit- 
ish Association,  called  the  Ohm,  which  is  equivalent  to 
about  -rV  of  a  mile  of  galvanized  No.  9  iron  wire,  such 
as  is  usually  employed  in  the  construction  of  telegraph 
lines.     This  standard  unit  of  resistance  is  now  made  use 
of  by  the  English  electricians. 

44.  EESISTAXCE  COILS. — As  no  battery  is  constant  in 
its  power,  and  no  magnet  uniform  in  its  strength,  neither 
of  these  can  be  made  use  of  as  an  accurate  basis  of  com* 
parison.     Resistance  coils,  composed  of  wire  of  certain 
alloys  of  metals,  carefully  prepared,  have  been  found 
not  to  vary  T  <r<nhnnr  in  eight  years.     The  only  variation 
is  that  due  to  difference  in  temperature,  which  may  be 
readily  calculated  and  allowed  for  when  necessary. 

It  will,  therefore,  be  understood  that  the  ohm  is  a  unit 
of  resistance  in  the  same  manner  that  an  inch  is  a  unit 
of  length,  or  a  pound  a  unit  of  weight. 


45.  A  TELEGRAPHIC  CIRCUIT,  in  its  simplest  form,  is 
shown  in  fig.  9.  A  and  B  represent  two  stations.  The 
circuit  may  be  traced  as  follows :  From  the  +  pole  of 
the  battery  E  to  the  key  K  (52)  and  electro-magnet  M, 
thence  through  the  line  L  to  the  other  station,  electro- 
magnet M'  and  key  K'  to  the  earth  at  G',  and  thence 
through  the  earth,  as  represented  by  the  dotted  line,  to 
the  —  pole  of  the  battery  E.  A  continuous  current  will 


26 


MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 


therefore  flow  through  the  circuit  as  long  as  it  remains 
uninterrupted,  and  the  armatures  of  the  electro-magnets 
M  and  M'  will  be  attracted  by  the  cores,  but  if  the  cir- 
cuit be  broken  by  means  of  one  of  the  keys,  K  or  K', 
both  electro-magnets  will  be  demagnetized.  Thus,  the 
breaking  of  the  circuit  at  either  station  affects  the  elec- 
tro-magnets of  both,  as  they  are  in  the  same  circuit. 

46.  THE  EARTH  CIRCUIT. — In  thus  using  the  earth  as 
part  of  the  circuit,  it  is  found  that  it  offers,  practically, 
no  resistance  to  the  passage  of  the  current.     Although 
comparatively  a  poor  conductor,  it  is  an  infinitely  large 
one  in  proportion  to  the  wire,  and,  therefore,  its  resis- 
tance is  not  appreciable  (42). 

47.  ARRANGEMENT  OF  BATTERIES. — In  practice  it  is 
usual  to  divide  the  battery  E  into  two  parts,  placing 
half  at  each  end  of  the  line,  for  reasons  which  will 
hereafter  appear.     It  is  important,  however,  when  this 
is  done,  that  the  positive  pole  of  one  battery  should 
be  connected  with  the  negative  pole  of  the  other,  other- 
wise they  would  neutralize  each  other,  and  no  effect 
would  be  obtained.     In  such  a  case  the  batteries  are 
said  to  be  reversed. 

48.  INTERMEDIATE  STATIONS. — It  is  evident  that  in- 
termediate stations  may  be  introduced  at  any  point 
upon  the  line  shown  in  the  above  figure,  each  being 
provided  with  an  electro-magnet  and  key,  forming  part 
of  the  circuit,  and  that  the  breaking  and  closing  of  the 
circuit  at  any  of  these  points  will  affect  all  the  electro- 
magnets through  which  it  passes,  in  the  same  manner 
and  at  the  same  instant  of  time. 

Any  desired  number  of  intermediate  stations  may 
be  placed  upon  a  line  until  the  combined  resistance  of 
their  electro-magnets  reduces  the  strength  of  the  cur- 
rent below  that  required  for  the  convenient  working  of 
the  circuit. 

49.  THE  MORSE  SYSTEM. — The  principle  of  the  Morse 
system  of  telegraphy  consists  in  conveying  arbitrary 
signals  by  means  of  the  magnetization  and  demagneti- 
zation of  an  electro-magnet,  by  the  alternate  breaking 


TELEGRAPHIC    CIRCUITS. 


and  closing  of  a  voltaic  circuit  in  the  manner  above  ex- 
plained. The  conventional  alphabet  used  in  America 
for  this  purpose  is  given  in  another  part  of  this  work. 

50.  OTHER  TELEGRAPHIC  SYSTEMS.  —  The  type  print- 
ing telegraph,  employing  the  "  Combination"  instrument 
of  Phclps,  is  the  only  system  other  than  the  Morse  now 
in  use  upon  the  public  lines  in  the  United  States.  The 
limited  extent  to  which  it  is  employed  renders  it  unneces- 
sary to  give  a  detailed  description  of  its  construction 
and  mode  of  operation  in  a  work  of  this  kind.  The 
electro-chemical  telegraph  of  Bain,  and  the  beautiful 
type-printing  instruments  of  House  and  Hughes,  were 
formerly  extensively  employed  in  this  country.  The 
former  has  now  given  place  to  the  Morse,  while  the  two 
latter  have  been  superseded  by  the  equally  rapid  and 
more  simple  and  effective  instrument  of  Phelps. 

In  addition  to  these,  the  magneto-electric  dial  instru- 
ment of  Edmands  &  Hamblet,  and  the  electro-magnetic 
alphabetical  instrument  of  Chester  are  finding  exten- 
sive employment  upon  private  lines,  where  extreme 
rapidity  of  transmission  is  not  required,  thus  rendering 
the  employment  of  skilled  operators  in  such  cases  un- 
necessary. 


CHAPTER   IY. 

THE  MORSE,  OR  AMERICAN  TELEGRAPHIC  SYSTEM. 

51.  THE  Morse  Telegraphic  Apparatus  consists  of  a 
signal  key  for  breaking  and  closing  the  circuit,  and  an 
electro-magnet,  the  armature  of  which  is  attached  to  a 
lever  carrying  a  steel  point  or  stvle,  which  embosses  a 
mark  upon  a  narrow  strip  of  paper,  moved  uniformly 
along  by  clock-work.  As  long  as  a  current  continues 
to  flow  through  the  coils  of  the  electro-magnet  the 
armature  is  attracted,  and  a  mark  is  made  upon  the 
moving  paper.  As  soon  as  the  circuit  is  broken  the 
armature  ceases  to  be  attracted,  and  is  withdrawn  from 
contact  with  the  paper  by  means  of  a  spring.  The 
duration  of  the  current,  and  consequently  the  length  of 
the  mark,  depends  upon  the  duration  of  the  contact  made 
by  the  key. 


Fio.  10. 

52.  THE  MORSE  SIGXAL  KEY  is  shown  in  fig.  10.*  It 
consists  of  a  brass  lever,  A,  four  or  five  inches  in  length, 
which  is  hung  upon  a  steel  arbor,  G,  between  adjustable 
set  screws,  I)  1),  in  such  a  manner  as  to  allow  it  ta 
move  freely  in  a  vertical  direction.  This  movement, 
however,  is  limited  in  one  direction  by  the  anvil  C,  and 
in  the  other  by  the  adjustable  set-screw,  F. 

*  The  drawings  of  the  signal  key,  register  and  relay  (figs.  10, 11  and  12),  are  from 
instruments  manufactured  by  Bradley. 


THK  MORSE,  OR  AMERICAN   TELEGRAPHIC    SYSTEM.  29 

One  wire  of  the  main  circuit  is  connected  to  the 
metallic  frame  of  the  key,  and  the  other  to  the  anvil,  C, 
which  is  insulated  from  the  frame.  These  connections 
arc  made  by  screws  passing  up  through  the  table  from 
beneath.  The  lever  is  provided  with  a  knob  of  vulcan- 
ite, B,  by  means  of  which  it  may  be  pressed  down  by 
the  finger  of  the  operator,  bringing  the  lever  in  contact 
with  the  anvil,  and  thus  closing  the  circuit,  precisely  as 
if  the  wires  themselves  had  been  brought  together.  The 
points  of  contact  between  the  lever  and  the  anvil  are 
made  of  platina,  as  ordinary  metals  would  be  fused  by 
the  passage  of  the  electric  spark  when  the  circuit  is 
broken.  A  spring  beneath  the  lever  restores  it  to  its 
original  position  when  the  pressure  of  the  operator's 
finger  is  withdrawn.  When  the  key  is  not  in  use  the 
circuit  is  completed  by  bringing  the  lever  of  the  cir- 
cuit closer,  H,  into  contact  with  the  anvil,  C. 


FlQ/ll. 

53.  THE  MORSE  REGISTER. — Fig.  11  represents  the 
recording  apparatus,  usually  termed  a  register,  which  is 
made  in  several  different  forms,  all  involving  the  same 
principles.  M  is.  the  electro-magnet,  the  two  ends  of 
the  wire  forming  the  coils  fyeing  carried  to  the  terminal 
binding  screws  on  the  base\  one  of  which  is  shown  at 
s,  to  which  the  conducting  wires  are  attached.  Above 
the  electro-magnet  is  seen  the, %  armature  attached  to 
the  lever  L,  which  moves  upon  an.arbor  at  d.  The  op- 
posite extremity  of  the  lever  carries  a  steel  point,  p. 


3(j  If  ODZRX  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

The  strip  of  paper  passes  through  the  guide  g  and  be- 
tween the  grooved  rollers  r  r,  which  are  moved  by 
a  train  of  wheels  driven  by  a  weight  attached  by  a  cord 
to  the  drum,  W. 

When  the  armature  is  attracted  by  the  magnet  the 
style  p  is  brought  forcibly  in  contact  with  the  paper, 
moving  above  it  upon  the  grooved  roller,  and  a  raised 
line  is  embossed  upon  it  corresponding  in  length  to  the 
time  the  armature  remains  attracted.  A  spring  ad- 
justed by  the  nut  n  withdraws  the  lever  when  the  at- 
traction ceases.  The  movement  of  the  lever  is  limited 
by  the  adjustable  screw,  m.  The  screw  c  regulates  the 
pressure  of  the  rollers  upon  the  paper,  and  the  clock- 
work is  started  and  stopped  by  the  brake  a.  The 
weight  is  wound  up  occasionally,  as  required,  by  the 
operator. 

54.  The  Morse  instrument  is  worked  either  by  the 
main  line  current  or  \>y  relay.     For  a  distance  not  ex- 
ceeding 20  or  30  miles,  a  register,  whose   coils   are 
wound  with  No.  30  copper  wire,  may  be  worked  by  the 
line  current,  if  the  line  be  well  insulated  (57). 

55.  When  the  insulation  is  defective,  or  the  circuit 
so  long  that  its  resistance  renders  the  current  too  weak 
to  work  a  register  direct,  as  is  usually  the  case  with 
telegraph  lines,  it  becomes  necessary  to  employ  a  re- 
ceiving magnet  or  relay,  which  brings  a  local  battery 
(11)  into  action  at  the  receiving  station,  the  current  of 
which  operates  the  register. 


FIG.  12. 

56.  THE  RELAY  MAGNET. — The  construction  of  the 
relay  is  shown  in  fig.  12.     M  is  the  electro-magnet, 


•THE  MORSE,  OR  AMERICAN  TELEGRAPHIC  SYSTEM.  £[. 

which  is  placed  in  a  horizontal  position,  and  is  movable 
by  means  of  the  screw  a.  The  coils  of  the  magnet  are 
of  fine  wire,  usually  from  No.  30  to  No.  36  in  size,  of 
great  length  and  closely  wound.*  The  ends  are  con- 
nected to  the  line  circuit  by  the  binding  screws,  m  m'. 
The  armature  lever  b  is  connected  with  the  binding 
screw  /  by  a  wire  carried  underneath  the  base  of  the 
instrument.  A  platina  point,  c,  on  the  armature  lever, 
is  brought  in  contact  with  a  similar  point  on  the  end  of 
the  screw  d  whenever  the  armature  is  attracted  by 
the  magnet,  the  screw  being  in  metallic  connection  with 
the  binding  screw  /',  by  means  of  the  frame  of  the  appa- 
ratus and  a  wire  beneath  the  base.  One  of  the  screws, 
1 1',  is  connected  to  one  pole  of  the  local  battery  (11), 
and  the  other  to  the  other  pole,  embracing  the  register 
magnet  in  its  circuit.  Therefore,  whenever  the  arma- 
ture is  attracted  by  the  force  of  the  main  current  acting 
upon  the  relay  magnet,  the  circuit  of  the  local  battery 
is  completed  through  the  register,  As  the  relay  is  con- 
structed with  great  delicacy,  a  feeble  line  current  is 
enabled  to  actuate  a  register  powerfully  through  the 
intervention  of  a  local  battery. 

The  movement  of  the  armature  is  regulated  to  corres- 
pond with  the  varying  strength  of  the  line  current  by 
means  of  the  adjustable  spiral  spring  /.  The  magnet 
may  be  also  set  at  any  required  distance  from  the  arma- 
ture by  means  of  the  screw  a,  which  is  cut  with  a  right 
and  left  hand  thread,  passing  through  the  soft  iron  bar 
connecting  the  two  cores,  and  also  through  the  support- 
ing post  in  the  rear  of  the  coils.  The  latter  slide  through 
openings  in  the  upright  metallic  plate  which,  supports 
the  adjustable  platina  pointed  screw  d. 

*  In  tho  instruments  manufactured  by  Dr.  Bradley  the  helices  or  coils  of  the 
electro-magnets,  instead  of  being  composed  of  silk  insulated  copper  wire,  as  de- 
scribed in  §  34,  are  made  of  naked  wire,  ingeniously  wound  by  accurate  machinery 
in  such  a  manner  that  the  convolutions  are  separated  from  each  other  by  a  space 
of  1-600  to  1-SOO  of  an  inch,  the  several  layers  being  insulated  frorn.  each  other  by 
thin  paper.  It  is  claimed  that,  by  this  method  of  winding,  a  coil  cf  a  given  length 
nnd  g;iU£e  of  wire,  and,  consequently,  of  a  given  resistance,  can  be  made  of  much 
less  diameter  than  is  possible  with  silk  insulated  wire,  while,  at  the  same  time,  the 
number  of  convolutions  will  bo  increased  as  well  as  the  power  of  the  electro- 


32  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

Fig.  13  represents  a   Pocket  Relay,  as  it  is  usually 
termed,  although  it  is  properly  a  main  line  sounder  (57). 


This  is  provided  with  a  key,  as  shown  in  the  figure,  the 
whole  being  conveniently  and  compactly  arranged  to  fit 
into  an  oval  case  four  or  five  inches  long,  which  may  be 
carried  in  the  pocket  It  is  an  extremely  convenient 
apparatus  for  line  repairers.  The  cut  shows  the  ar- 
rangement manufactured  by  the  Messrs.  Chester. 


FIG.  14. 

67.  THE  SOUNDER. — In  many  of  the  larger  telegraph 
offices  the  recording  apparatus  is  dispensed  with,  and 
the  communications  read  by  the  sound  of  the  armature 
lever.  In  that  case  the  Sounder  (fig.  14)  is  employed  in 
the  place  of  the  register,  the  connections  of  the  wires 
being  arranged  in  precisely  the  same  manner.  The 
Sounder  consists  simply  of  the  electro-magnet,  arma- 


THE  MORSE,  OR  AMERICAN  TELEGRAPHIC  SYSTEM.  33 

ture  and  lever,  fixed  upon  a  base.*     The  coils  are  usu- 
ally wound  with  ]STo.  23  wire. 

Main  Line  Sounders  are  used  in  some  offices,  which 
enables  the  operator  to  dispense  with  the  local  battery. 
The  coils  are  wound  with  line  wire,  usually  No.  80,  and 
are  frequently  made  somewhat  larger  than  those  of  the 
relay.  A  common  form  of  this  instrument  is  known  as 
the  "Box  Sounder."  The  lever,  striking  upon  a  hollow 
wooden  box  containing  the  magnet,  gives  a  sound  that 
may  easily  be  distinguished  by  the  operator  under  ordi- 
nary circumstances. 


Fig.  15  (8.  F.  Day  &  Co.)  shows  an  excellent  form  of 
Main  Line  Sounder.  The  parts  of  the  instrument  are 
mounted  upon  a  metallic  plate,  the  centre  of  which  is 
raised  slightly  above  the  base,  so  as  to  form  a  bridge,  as 
shown  in  the  cut.  The  armature  lever  is  of  steel,  and 
the  whole  arrangement  is  well  adapted  to  increase  the 
sound  of  the  lever  as  much  as  possible — a  feature  of  great 
value  in  working  with  weak  currents  or  on  badly  insu- 
lated lines.  These  instruments  are  also  made  in  seve- 
ral other  forms,  and  various  devices  for  increasing  the 
sound  of  the  lever  arc  made  use  of.  On  many  lines 
they  are  found  to  answer  as  well  as  the  usual  arrange- 
ment, employing  a  relay  and  local  battery. 

*  The  instrument  shown  in  the  figure  is  from  the  manufactorj  of  C.  T.  &  J.  N. 
Chester.  3       ~;  ."«*K 


34 


MODERN  PRACTICE  OF  THE  ELECTRIC  TELE.GRAPH. 


For  circuits  of  moderate  length  a  Main  Line  Register 
(fig  16),  manufactured  by  Day  &  Co.,  has  been  employed 
with  excellent  results. 


58.  ARRANGEMENT  OF  A  TERMINAL  STATION. — Fig.  17 
is  a  diagram  showing  the  arrangement  of  wires,  batteries, 


Fio.  17. 

and  instruments  for  one  of  the  terminal  stations  of  a 


RELAY    MAGNET. 


LOCAL    SOUNDER. 


COMBINATION    MAIN    LINE    INSTRUMENT. 
Manufactured  bg  L.  0.  Tittotson  &  Co.,  New  York. 


THE  MORSE,  OB  AMERICAN  TELEGRAPHIC  SYSTEM. 


35 


line.  The  line  wire  L  first  enters  the  lightning  arrester 
X,  and  passes  thence  through  the  coils  of  the  relay  M 
by  the  binding  screws,  1,  2,  and  thence  to  the  key  K, 
main  battery  E,  and  finally  to  the  ground  at  G.  The 
local  circuit  commences  at  the  +  pole  of  the  local  bat- 
tery E'  and  through  the  platina  points  of  the  relay  by 
the  binding  screws,  3,  4,  thence  through  the  register 
or  sounder  coils,  S,  and  back  to  the  other  pole  of  the 
battery. 


59.  ARRANGEMENT  OF  A  WAY  STATION.— Fig.  18 
shows  a  plan  of  the  instruments  and  connections  at  a 
way  station.  The  line  enters  at  L,  passes  through  the 
lightning  arrester  X  (70),  and  thence  through  the  relay 
M,  key  K,  and  back  to  the  lightning  arrester,  and 
thence  to  the  next  station  by  the  line  L'.  The  arrange- 
ment of  the  local  circuit  is  the  same  as  in  the  last  figure. 
The  button  C,  arranged  as  shown  in  the  figure,  is  called 
a  "  cut-out"  (62).  When  turned  so  as  to  connect  the  two 
wires  leading  into  the  office,  it  allows  the  line  current 
to  pass  across  from  one  to  the  other  without  going 
through  the  instruments.  The  instruments  should 
always  be  cut  out  by  means  of  this  apparatus  when 
leaving  the  office  temporarily,  or  for  the  night,  and 


36  MODERN  PRACTICE  OF  THE  ELECTIUC  TELEGRAPH. 

also  during  a  thunder  storm,  to  avoid  damage  to  the 
apparatus.  Fig.  21  shows  a  better  arrangement. 

The  G-round  Switch,  Q  (63),  is  used  to  connect  the 
line  with  the  earth  on  cither  side  of  the  instruments  at 
pleasure.  It  is  only  used  in  case  of  accidents  or  inter- 
ruptions on  the  lines,  as  will  be  hereafter  explained. 

60.  ADJUSTMENT  OF  THE  APPARATUS. — The  princi- 
pal difficulties  which  the  operator  is  liable  to  meet  with 
in  working  the  Morse  apparatus  are  as  follows  : 

1.  When  the  paper  in  the  register  does  not  run  freely 
from  the  reel  on  which  it  is  held,  or  sticks  in  the  guides 
from  irregularity  in  width,  or  if  the  style  is  adjusted  to 
indent  the  paper  too  deeply,  the  paper  moves  irregu- 
larly, shortening  dashes  into  dots,  and  causing  dots  to 
run  together. 

2.  The  style  should  be  adjusted  so  as  to  move  freely 
in  the  groove  of  the  upper  roller,  or  the  marks  will  be 
more  or  less  indistinct.     If  it  is  completely  out  of  the 
groove,  no  marks  will  be  produced.    These  faults  gene- 
rally arise  from  too  much  end  play  in  the  pivots  of  the 
lever,  or  from  the  pivot  screws  working  loose.     When 
the  lever  works  too  loosely  in  its  bearings,  irregular 
dashes,  too  deep  at  their  commencement,  and  tapering 
off  to  nothing,  will  be  produced. 

Residuary  magnetism  sometimes  causes  the  armature 
of  the  electro-magnet  to  stick.  This  will  always  hap- 
pen if  the  armature  is  allowed  to  touch  the  poles  of  the 
magnet.  The  screw  stop  should  therefore  be  adjusted 
so  as  to  prevent  the  armature  from  approaching  too 
closely  to  the  poles  of  the  magnet.  The  upper  screw 
stop,  which  regulates  the  play  of  the  lever,  should  be 
adjusted  so  that  the  movement  is  just  sufficient  to  with- 
draw the  style  from  contact  with  the  paper. 

3.  If  the  paper  runs  between  the  rollers  "crooked,"' 
the  pressure  of  the  upper   roller  upon   the   paper   is 
greater  at  one  end  than  the  other.    This  pressure  is  re- 
gulated by  two  springs,  one  on  each  side  of  the  iristr.i- 
ment,  and  they  should  be  made  as  nearly  equal  in  pres- 
sure as  possible. 


THE  MORSE,  OR  AMERICA*    TELEGRAPHIC    SYSTEM.  %*J 

4;  When  the  signs  are  confused  the  relay  requires 
adjustment  to  suit  the  strength  of  the  current. 

5.  If  the  relay  moves  by  the  action  of  the  line  cur- 
rent, and  the  register  or  sounder  does  not  act,  the  fault 
is  somewhere  in  the  local  circuit.     If  the  register  does 
not  work  when  the  relay  is  moved  by  the  linger,  the 
local  circuit  is  certainly  at  fault,  either  from  weakness 
of  the  local  battery,  a  loose  connection,  a  broken  wire, 
or  dirt  between  the  platina  points  of  the  relay.     The 
latter  should,  when  too  much  corroded,  be  cleaned  care- 
fully with  emery  paper,  taking  care  to  remove  as  little 
of  the  platina  as  possible. 

6.  The  sticking  of  the  key,  which  sometimes  occurs,  is 
caused  either  by  the  platina  points  becoming  oxidized 
and  dirty,  or  by  small  particles  of  metal  and  dirt  collect- 
ing behind  the  circuit  closer  and  about  the  anvil,  caus- 
ing a  partial  connection  when  the  key  is  open. 

7.  It  is  very  important  that  all  the  connections  about  an 
office  should  be  firmly  screwed  up.     Neglect  of  this  pre- 
caution is  a  very  prolific  cause  of  trouble  upon  a  tele- 
graph line. 

8.  In  rainy  weather,  or  when  the  insulation  of  the 
line  is  defective  from  any  cause,  the  cores  of  the  relay 
must  be  withdrawn  to  a  greater  distance  from  the  ar- 
mature, to  avoid  the  influence  of  the  residual  magnet- 
ism, caused  by  the  escape  of  the  "current"  from  the 
line.     This  is  called  "adjusting"  the  instrument,  and  is 
one  of  the  most  important  of  an  operator's  duties,  re- 
quiring great  judgment  and   skill  during  unfavorable 
weather  and  on  poorly  insulated  lines.    The  key  should 
never  be  opened  without  carefully  adjusting  the  relay, 
to  be  sure  that  no  other  offices  are  using  the  line. 

SWITCHES    OR    COMMUTATORS. 

61.  These  are  employed  for  the  purpose  of  connect- 
ing one  circuit  with  another,  for  dividing  a  circuit  into 
two  parts,  or  in  short,  for  any  purpose  where  it  is  neces- 
sary to  alter  the  connections  of  a  line  or  circuit. 

62.  Fig>  19  shows  the  simple  Button  or  Circuit  Ckser, 


33 


MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 


which  is  usually  employed  as  a  "  cut  out"  (58).  The 
base  A  is  of  wood  or  hard  rubber.  The  brass  lever,  B, 
when  in  the  position  shown  in  the  figure,  forms  an  elec- 
trical connection  between  the  metallic  studs  C  C,  which 


FIG.  19. 

are  continuous  with  the  screws,  D  D,  passing  through  the 
table  and  terminating  in  binding  screws,  to  which  the 
wires  are  attached.  The  spring  F,  pressing  against 
the  lever,  insures  a  firm  contact  with  the  studs.  This 
circuit  closer  is  sometimes,  for  special  purposes,  made 
with  four  connections  instead  of  two. 


63.  Fig.  20  represents  a  Ground  Switch  (58).   The  lever 


THE  MORSE,  OR  AMERICAN  TELEGRAPHIC  SYSTEM.  30 

A  is  attached  to  a  wire  leading  to  the  earth,  and  the  two 
studs,  B,  C,  are  connected  to  the  line  wire  on  each  side 
of  the  instruments. 


64.  THE  PLUG  SWITCH  is  shown  in  fig.  21.     This  ar- 
rangement  consists   of  a   brass  spring,  brought  very 
firmly  against  a  stationary  pin.     A  wedge  or  plug  made 
of  two  pieces  of  brass,  separated  by  an  insulating  mate- 
rial, is  made  in  the  form  shown,  to  admit  of  insertion 
between  the  spring  and  the  pin.     The  wires  leading  to 
the  instrument  are  attached  to  this  wedge  by  flexible 
conductors.     When  the  wedge  is  inserted,  the  line  cur- 
rent is  diverted  through  the  instrument,  but  is  not  in- 
terrupted.   The  instrument  may  readily  be  withdrawn 
from  the  line  by  taking  out  the  wedge,  the  spring  in- 
stantaneously closing  the  main  circuit.     This  arrange- 
ment is  found  extremely  useful  in  connecting  batter- 
ies as  well  as  instruments.     At  a  way  station  it  is 
preferable  to  a  simple  cut-out,  for  the  reason  that  the 
apparatus  is  entirely  disconnected  from  the  circuit  when 
the  wedge  is  withdrawn  (59). 

65.  THE  UNIVERSAL  SWITCH,  for  the   use  of  offices 
having  a  considerable  number  of  wires,  is  constructed 


40  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

in  several  different  forms,  although  the  principle   in- 
volved is  nearly  the  same  in  each.     Fig.  22*  represents 


the  arrangement  most  generally  used,  which  is  known 
as  the  Culgan  Switch,  from  the  name  of  its  inventor. 
The  upright  straps  of  brass,  A,  B,  C,  D,  E,  F,  are  fixed 
upon  a  slab  of  hard  wood,  or  other  non-conducting  ma- 
terial, and  provided  with  binding  screws  at  their  upper 
extremities,  for  the  reception  of  the  line  wires.  The 
binding  screws,  I,  II,  III,  IV,  V,  VI,  are  in  electrical 
connection  with  the  horizontal  rows  of  buttons,  by  wires 
underneath  the  board,  not  shown  in  the  figure.  Thus, 
any  wire  attached  to  one  set  of  binding  screws  may 
readily  be  connected  with  any  wire  attached  to  the  other 
set,  by  simply  turning  the  appropriate  button.  A  row 
of  metallic  pegs,  x  x\  are  so  arranged  that  either  of  the 
upright  straps  may  be  separated  into  two  parts  by  the 
withdrawal  of  the  peg  belonging  to  it,  as  shown  at  x. 
The  object  of  this  device  will  be  explained  hereafter. 

This  switch  may  be  made  of  any  size  and  with  any 
number  of  connections,  depending  upon  the  number  of 
lines  it  is  designed  to  accommodate.  The  wires  may  be 
attached  to  it  in  a  number  of  different  ways,  the  parti- 

*  L.  G.  Tillotson  &  Co.,  New  York. 


THE  MORSE,  OR  AMERICAN  TELEGRAPHIC    SYSTEM.  ^ 

cular  arrangement  adopted  in  each  case  depending  upon 
the  nature  of  the  changes  required  to  be  made. 

66.  ARRANGEMENT  OF  THE  CONNECTIONS. — The  switch 
shown  in  the  figure,  placed  at  a  way  station,  could  be 
arranged  to  accommodate  three  through  wires,  and  an 
equal  number  of  instruments,  providing  for  all  the  ne- 
cessary changes.     The  arrangements  in  this  case  would 
be  as  follows  :  Connect  line  wires  Nos.  1,  2  and  3,  east, 
with  A,  B  and  C  ;  1 ,  2  and  3,  west,  with  D,  E  and  F. 
Instrument  No.  1  to  I  and  II,  No.  2  to  III  and  IV, 
No.  3  to  V  and  YI.     Turn  the  buttons  so  as  to  connect 
A  with  I  and  D  with  II.     The  circuit  of  No.  1  wire  will 
then  enter  at  A,  go  to  instrument  No.  1  via  I,  returning 
to  II,  and  thence  going  out  at  D.     The  other  instru- 
ments may  be  connected  at  pleasure  in  the  same  man- 
ner.    If  it  is  desired  to  connect  a  circuit  through,  for 
instance  No.  1,  leaving  the  instrument  out  of  circuit,  it 
is  done  by  turning  the  buttons  so  as  to  connect  both  A 
and  D  to  the  same  horizontal  wire,  either  I  or  II.     By 
a  little  study  it  will  be  seen  that  any  wire  cast  may  be 
connected  with  any  other  wire  west,  with  or  without 
any  desired  instrument,  at  pleasure.     The  ground  wire 
is  attached  at  VII,  and  may  be  connected  with  any  line 
wire  east  or  west  at  pleasure. 

67.  The  same  switch,  placed  at  a  terminal  station,' 
would  provide  for  six  wires,  by  connecting  them  as  be- 
fore to  the  screws  A,  B,  C,  D,  E,  F,  and  the  instruments 
to  I,  II,  III,  IV,  V,  VI.     The  wires  of  a  loop  (87)  may 
be  connected  to  I  and  II  in  place  of  the  instrument, 
and  may  be  put  in  circuit  with  any  wire  by  turning  the 
buttons  connected  with  I  and  II  both  on  to  the  corres- 
ponding strap,  which  is  then  divided  by  withdrawing- 
the  peg,  forcing  the  current  to  pass  through  the  loop.' 
Extra  sets  of  buttons  for  loops  are  usually  provided 
when  the  switch  is  intended  for  a  terminal  station,  which 
can  be  used  without  diminishing  the  capacity  of  the 
switch  for  other  purposes. 

68.  JONES'  LOCK  SWITCH  is  employed  for  the  same* 
purposes,  and  connected  in  the  same  mariner  as  the  on# 


42  MODERN  PRACTICE  OF  THE  ELECTRIC   TELEGRAPH. 

last  described,  but  the  connection  between  the  vertical 
and  horizontal  wires  is  made  by  a  metallic  peg,  provided 
with  a  spring,  as  shown  in  fig.  23  (Chester).  This  ar- 
rangement entirely  obviates  the  danger  of  imperfect 
connections,  from  the  loosening  of  buttons,  etc.,  which 
is  sometimes  a  source  of  trouble  in  the  Culgan  Switch. 


FIG.  23. 

It  is  also  cheaper  and  much  more  compact ;  a  matter  of 
some  importance  in  arranging  for  the  accommodation  of 
a  large  number  of  wires. 

69.  There  are  other  forms  of  switches  designed  for 
special  purposes,  which  it  is  unnecessary  to  describe  in 
a  work  of  this  kind.     Those  already  referred  to  are  all 
that  are  generally  required  in  fitting  up  a  telegraph 
station. 

LIGHTNING  ARRESTERS. 

70.  The   danger  of  injury  to  the  instruments   and 
operators  at  a  telegraph  station,  by  atmospheric  elec- 
tricity, is  usually  guarded  against  by  the  use  of  an 
apparatus  termed  the  Lightning  Arrester,  which  is  con- 
structed in  accordance  with  the  well  established  fact 
that  this  kind  of  electricity,  being  possessed  of  enor- 
mous intensity,  prefers  a  short  route  through  a  poor 
conductor  to  a  longer  one  through  a  good  conductor, 
while  the  comparatively  low  intensity  of  the  voltaic 


THE  MORSE,  OR  AMERICAN  TELEGRAPHIC   SYSTEM.  43 

current,  used  for  telegraphic  purposes,  confines  it  to 
the  conducting  wires. 

71.  THE  PLATE  ARRESTER. — The  arrester  most  usu- 
ally employed  upon  the  telegraph  lines  in  this  country 
consists  of  a  flat  plate  of  brass,  about  five  or  six  inches 
in  length,  which  is  attached  to  the  "ground  wire." 
Other  plates  of  brass  rest  upon  this,  being  separated 
from  it  by  a  thin  sheet  of  insulating  material.  These 
last  mentioned  plates  are  provided  with  binding  screws, 
for  the  attachment  of  the  line  wires.  Any  surplus 
charge  of  atmospheric  electricity,  entering  by  the  line 
wires,  forces  its  way  through  the  insulating  material  into 
the  ground  plate,  and  is  thus  carried  off  to  the  ground 
without  injuring  the  apparatus.  The  form  of  arrester 
supplied  by  the  Messrs.  Chester  is  shown  in  fig.  24. 


The  plates  in  connection  with  the  line  wires  are 
firmly  held  in  their  places  by  a  wooden  cross  piece, 
secured  by  screws  at  each  end,  as  shown  in  the  cut.  A 
thin  sheet  of  gutta  percha,  or  paper,  is  used  to  separate 
the  plates.  When  paper  is  used  it  should  be  saturated 
with  paraffine.  Mica  is,  perhaps,  better  than  either,  as 
it  is  not  carbonized  by  the  passage  of  the  spark,  as  pa- 
per sometimes  is,  so  as  to  form  a  ground  connection. 
The  manner  in  which  the  arrester  is  connected  with  the 
wires  leading  into  an  office  will  be  seen  by  reference  to 
fig.  18,  where  the  two  line  wires,  L  and  L',  are  attached 
to  the  two  upper  plates  of  the  arrester,  X,  while  a  wire 
leading  to  the  ground  at  G  is  attached  to  the  lower  plate. 

72.  BRADLEY'S  ARRESTER.— Another  form  of  arrester, 


44  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPK.  ! 

designed  by  Dr.  Bradley,  is  shown  in  fig.  25,  and  lias 
recently  been  quite  extensively  employed,  with  excel- 
lent results. 


It  depends  for  its  action  upon  the  well  ascertained 
fact  that  lightning  always  passes  from  a  point  to  a  plate 
with  great  facility.  The  line  wires  leading  into  the 
office  are  attached  to  the  metallic  plates  A  and  B  by 
means  of  binding  screws  beneath,  the  ground  wire  being 
attached  in  the  same  manner  to  the  plate  C.  Platina 
tipped  screws,  1,  2,  3,  4,  are  fixed  to  each  plate,  and 
are  adjusted  so  as  to  come  nearly  in  contact  with  the  op- 
posite plate.  As  lightning  occasionally  passes  from  the 
earth  to  the  clouds,  as  well  as  from  the  clouds  to  the 
earth,  this  arrester  is  so  arranged  as  to  facilitate  its 
passage  in  either  direction.  The  buttons,  F  F,  are  so 
arranged  that  the  apparatus  serves  for  a  "cut-out"  and 
a  "ground  switch"  as  well  as  an  arrester.  Its  appli- 
cation to  these  purposes  will  be  at  once  understood  by 
an  inspection  of  the  cut.  This  form  of  arrester  is 
peculiarly  well  adapted  for  the  protection  of  cables,  or 
any  situation  where  it  is  exposed  to  accidental  damp- 
ness, as  it  is  much  less  apt  to  interfere  with  the  work- 
ing of  the  line  in  such  cases  than  the  plate  arrester  pre- 
viously described. 

73.  Lightning  arresters  must  always  be  kept  free 
from  dampness  and  dirt,  as  far  as  practicable.  Much 
annoyance  often  arises  from  neglect  of  this  precaution, 
as  moisture  between  the  plates  will  often  cause  a  seri- 
ous escape,  greatly  interfering  with  the  working  of  the 
line.  This  difficulty  is  especially  liable  to  occur  where 
the  arresters  are  used  for  the  protection  of  submarine 
cables.  A  flash  of  atmospheric  electricity  also  fre- 


THE  MORSE,  OB  AMERICAN  TELEGRAPHIC  SYSTEM.  45 

.quently  carbonizes  the  paper  between  the  plates,  or 
fuses  the  metal,  so  as  to  permanently  connect  the 
ground  and  the  line.  Consequently,  the  lightning  ar- 
resters should  be  frequently  taken  apart  and  examined. 
This  should  invariably  be  done  after  a  thunder  storm. 

REPEATERS. 

74.  When  the  length  of  a  telegraphic  circuit  exceeds 
a  certain  limit,  depending  upon  the  insulation,  the  size 
of  the  conductor,  the  number  of  instruments  in  circuit, 
etc.,  the  line  current  becomes  so  enfeebled,  even  when 
large  batteries  are  employed,  that  satisfactory  signals 
cannot  be  transmitted.  In  such  cases  it  was  formerly 
customary  to  re-write  the  messages  at  some  interme- 
diate station,  but  this  duty  is  now  usually  performed  by 
an  apparatus  called  a  repeater.  The  principle  of  this 
arrangement  consists  in  causing  the  sounder  or  register 
connected  with  one  circuit  to  open  and  close  the  circuit 
of  another  line  by  an  action  similar  to  that  of  a  relay 
(56).  Repeaters  are  also  often  used  for  connecting  one 
or  more  branch  lines  with  a  main  line,  for  the  purpose 
of  transmitting  press  news,  etc.,  simultaneously  to  dif- 
ferent places.  This  enables  all  the  stations  in  connec- 
tion to  write  to  each  other  as  readily  as  if  they  were 
situated  upon  the  same  circuit. 

Since  the  general  introduction  of  repeaters  it  has 
become  quite  practicable  to  telegraph  direct  between 
places  situated  at  very  great  distances  from  each  other. 
It  is  not  uncommon,  at  the  present  day,  to  work  direct 
through  four  or  five  thousand  miles  of  continuous  line 
by  the  aid  of  these  instruments  with  almost  as  much 
facility  as  if  it  were  one  continuous  circuit.  On  one  or 
two  occasions  the  stations  at  Heart's  Content,  New- 
foundland, and  San  Francisco,  California,  have  been 
placed  in  direct  communication  with  each  other,  the 
operators  at  these  widely  separated  points  conversing 
with  each  other  across  the  entire  breadth  of  the  conti- 
nent without  the  slightest  difficulty. 


46 


MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 


75.  WOOD'S  BUTTON  REPEATER. — This  is  the  simplest 

Fig.  26  shows 


arrangement  of  this  kind  now  in  use. 


the  most  convenient  and  serviceable  form  in  which  the 
button  or  switch,  and  its  connections,  can  be  arranged 
for  the  purpose  of  changing  the  circuits.  The  instru- 
ments, batteries,  &c.,  are  shown  in  outline,  for  conve- 
nience of  explanation.  M  and  M'  are  the  eastern  and 
western  relays,  S  and  S'  the  eastern  and  western  soun- 
ders. The  local  connections  are  not  shown,  but  are  run 
as  usual.  The  eastern  and  western  main  batteries  are 
shown  at  B  and  B',  and  are  placed  with  opposite  poles 
to  the  ground,  at  the  repeating  station,  so  that  when  the 
line  is  put  *;  through"  the  two  batteries  will  coincide. 

By  means  of  this  arrangement  the  following  result 
may  be  obtained  : 

I.  Two  distinct  and  independent  circuits.     The  lever  L 
remaining  in  the  position  shown  in  the  drawing  (marked 
1),  and  the  button  at  4,  closed. 

II.  A  through  circuit.     The  lever  L  remains  as  before, 
but  the  button  at  4  is  opened,  throwing  off  the  ground 
connection  between  the  two  batteries,  B  and  B'. 

III.  Two  distinct  circuits  arranged  for  repeating.     The 
button  at  4  is  closed.     If  the  lever  L  be  placed  in  tho 


THE  MORSE,  OR  AMERICAN   TELEGRAPHIC    SYSTEM.  47 

position  indicated  by  the  figures  '2,  2,  the  eastern  soun- 
der repeats  into  the  western  circuit.  If  the  lever  is 
changed  to  3,  3,  the  western  sounder  repeats  into  the 
eastern  circuit.  The  operator  in  charge  of  a  button 
repeater  will  find  his  duty  very  simple  if  he  governs 
himself  by  the  following 

RULE. — When  either  sounder  fails  to  work  coincident 
with  the  other,  turn  the  button  instantly. 

In  connecting  up  this  apparatus,  the  arrangement  of 
the  poles  of  the  main  batteries  above  specified  should 
be  carefull}r  borne  in  mind.  It  is  also  of  the  utmost 
importance  that  these  batteries  should  be  perfectly  in- 
sulated from  the  ground,  as  the  point  at  which  the  cir- 
cuit is  open  and  closed  is  between  the  battery  and  the 
ground.  Therefore,  an  escape  occurring  from  the  bat- 
tery to  the  ground  will  cause  a  residual  current  upon 
the  main  line,  when  the  circuit  is  open  at  the  repeat- 
ing points  of  the  sounder,  and  thus  interfere  with  its 
working. 

In  cases  where  it  is  not  required  to  work  the  two 
lines  through  in  one  circuit,  the  connections  are  ar- 
ranged differently  from  the  plan  shown  in  iig.  26,  the 
main  battery  being  placed  in  the  circuit  between  the 
lever  L  and  the  ground  Gr,  instead  of  at  B  and  B',  as 
shown.  In  this  case  the  switch  4  may  be  dispensed 
with  altogether. 

76.  The  lever  of  the  sounder  moves  through  a  certain 
space  before  closing  the  circuit  of  the  second  line,  so 
that  the  duration  of  the  current  sent  forward  is  shorter 
than  that  received  from  the  transmitting  station.     A 
second  repeater  shortens  it  still  more,  so  that  the  dots 
cease  to  be  repeated,  and  arc  frequently  lost  altogether. 
The  sending  operator  must  therefore  transmit  the  sig- 
nals more  firmly,  as  it  is  termed  ;  that  is,  increase  the 
length  of  the  key  contact,  especially  when  sending  dots. 
For  the  same  reason,  the  sounder  levers  in  a  repeating 
apparatus  should  be  adjusted  to  have  as  little  motion  as 
possible. 

77.  HICKS'  AUTOMATIC  REPEATER.— This  arrangement 


48 


MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 


dispenses  with  the  attendance  of  an  operator  for  the 
purpose  of  changing  the  circuits  while  working,  the  only 
attention  required  being  to  keep  the  relays  properly 
adjusted.  The  principle  of  the  apparatus  is  shown  in 
fig.  27. 


'  The  main  circuits  pass  through  the  relay  magnets  M 
and  M',  thence  to  the  repeating  points  /  g  and  f  g', 
attached  to  the  opposite  sounder  levers  respectively, 
and  thence  to  the  main  battery  and  ground  at  G  and 
G'.  The  platina  points  of  the  screws/  and/'  are  placed 
uponU  shaped  springs,  which,  in  a  great  measure,  pre- 
vents the  shortening  of  the  signals  referred  to  in  the 
last  paragraph.  The  local  circuits  are  run  through  the 
relay  points  b  arid  b'  and  the  sounders  R  and  R',  on 
each  side  of  the  apparatus,  in  the  ordinary  manner,  but 
to  prevent  confusion  of  lines,  are  omitted  in  the  draw- 
ing. The  "extra  local"  magnets,  L  and  L'  act  upon 
armatures  placed  upon  the  relay  levers  a  and  a,  oppo- 
site to  the  regular  armature.  (See  figure.)  These 
extra  local  magnets  are  movable  by  means  of  the  screws 
d  d',  and  the  adjustment  of  the  relays  M  M'  is  performed 
by  means  of  these  extra  local  magnets,  the  springs  s  s1 
not  being  used  for  this  purpose. 

In  the  figure  the  repeater  is  shown  in  its  normal 
position,  with  both  circuits  closed.     The  circuits  of  the 


THE  MORSE,  OR  AMERICAN  TELEGRAPHIC  STSTEM.  49 

extra  local  batteries  B  B'  (shown  by  dotted  lines)  pass 
through  the  sounder  levers  /  /',  the  screws  p  p',  and 
thence  respectively  to  the  extra  local  magnets  on  the 
opposite  side  of  the  apparatus.  These  magnets  must  be 
so  adjusted  that  their  attraction  is  not  sufficient  to  draw 
the  armatures  away  from  M  M'  unless  the  main  circuit 
is  broken. 

It  will  also  be  seen,  by  referring  to  the  drawing,  that 
when  the  main  circuit  is  broken  and  the  armature  falls 
back  on  the  point  c,  that  the  extra  local  magnet  L  is  cut 
out.  But  the  instant  this  happens  the  spring  s  draws 
the  armature  away  again.  As  soon  as  the  contact  is 
broken  at  c  there  is  a  circuit  through  L,  and  the  arma- 
ture is  again  drawn  back  to  c.  The  tension  of  the 
spring  s  being  but  just  sufficient  to  draw  the  armature 
away  from  c,  the  armature  vibrates  on  the  point  c  through 
such  a  small  space,  and  with  such  rapidity,  that  the 
motion  is  invisible  to  the  eye.  On  account  of  the  ex- 
treme rapidity  of  these  vibrations,  it  is  impossible  to 
close  the  main  circuit  at  a  time  when  the  extra  local 
magnet  L  is  not  cut  out,  and  the  armature  will  conse- 
quently obey  the  slightest  impulse  caused  by  the  attrac- 
tion of  the  relay  magnet. 

The  working  of  the  apparatus  requires  but  little  fur- 
ther explanation.  If  the  western  main  circuit  be  broken, 
for  instance,  the  armature  lever  a  falls  back  and  vibrates 
on  the  point  c,  as  above  described.  The  sounder  lever 
I  first  breaks  the  circuit  of  the  eastern  extra  local  mag- 
net L',  then  that  of  the  eastern  main  line,  which  passes 
through  the  relay  M.  The  circuit  through  both  L'  and 
M'  being  thus  broken,  the  slight  tension  of  the  spring  s' 
will  hold  the  armature  in  its  place,  and  prevent  the 
local  circuit  through  R,  and  consequentl}r  the  western 
main  circuit,  from  being  broken.  When  the  western 
circuit  is  again  closed  the  reverse  of  these  operations 
takes  place. 

78.  In  using  this  repeater  the  springs  s  s'  should  be 
adjusted  with  the  smallest  possible  amount  of  tension, 
just  sufficient  to  hold  the  armature  in  place.  When  once 


50 


MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 


adjusted  they  should  be  let  alone.  Care  must  be  taken 
that  none  of  the  wires  under  or  about  the  magnets  touch 
any  part  of  the  brass.  The  extra  local  magnets,  for 
example,  may  be  cut  out  entirely  in  this  way.  The 
screws  that  adjust  the  extra  local  magnets  should  be 
oiled  with  fine  oil  to  prevent  wear  and  make  their  ad- 
justment easy.  The  extra  local  batteries  must  be  kept 
of  a  uniform  strength  ;  if  they,  are  allowed  to  become 
weak  the  instrument  will  be  thrown  out  of  adjustment. 
79.  MILLIKEX'S  REPEATER. — In  the  general  arrange- 
ment of  its  connections  this  repeater  somewhat  resem- 
bles that  of  Hicks',  but 'is  more  simple  in  principle. 
Fig.  28  is  a  plan  of  its  connections.  The  main  line 
L  - ,  , 

WEST  n^fiHlfr1  \ 


EAST 


FIG.  28. 

wire  from  the  west  passes  through  the  relay  magnet  M 
and  the  repeating  points  f  g'  of  the  opposite  soun- 
der, and  thence  to  the  battery  and  ground  at  G'.  The 
eastern  line  passes  through  M',  /and  g  to  G,  in  a  simi- 
lar manner. 

The  extra  local  magnets  L  and  L'  are  arranged,  as 
shown  in  the  figure,  so  that  when  either  of  their  arma- 
tures is  released  it  is  drawn  back  by  the  spring  attached 
to  its  lever,  bringing  the  latter  firmly  in  contact  with 
the  armature  lever  of  the  corresponding  relay.  The 
extra  local  batteries  arc  shown  at  B  and  B'  the  circuit 


THE  MORSE,  OR  AMERICAN  TELEGRAPHIC  SYSTEM.  5^ 

of  each  being  indicated  by  dotted  lines.  The  ordinary 
local  circuit  through  the  relay  and  sounder  is  omitted, 
to  avoid  confusion  in  the  diagram. 

If  the  main  circuit  be  broken  in  the  western  wire, 
the  relay  M  breaks  the  local  circuit  of  the  sounder  R  at 
5.  The  movement  of  the  lever  /  of  the  sounder  first 
breaks  the  extra  local  circuit  at p,  causing  the  magnet 
L'  to  release  the  armature  d',  which  is  drawn  back  by 
the  spring  s'  against  the  top  of  the  lever  a,  and,  secondly, 
the  eastern  main  circuit,  is  also  broken  at  /.  g.  The 
lever  a  is  prevented  from  falling  back  when*  the  circuit 
of  M'  is  broken  by  the  tension  of  the  spring  s',  which  is 
so  adjusted  as  to  be  greater  than  that  of  the  spring  h '. 
The  apparatus  on  the  right  hand  side  of  the  repeater, 
therefore,  remains  quiet  while  the  west  is  working,  and 
vice  versa,  the  current  through  M'  being  always  restored 
before  that  through  L'  is  broken,  which  is  effected  by 
the  U  shaped  spring  on  the  screw/. 

One  of  the  principal  advantages  in  the  construction 
of  Milliken's  repeater  consists  in  the  fact,  that  any 
slight  variation  in  the  strength  of  the  extra  local  circuit, 
from  weakness  of  the  battery  or  other  causes,  does  not 
affect  the  adjustment  of  the  relay  magnets,  as  in  the 
case  with  Hicks'  repeater.  The  adjustment  and  action 
of  the  two  magnets  are  entirely  independent  of  each 
other,  as  will  be  seen  by  reference  to  the  diagram.  The 
relay  levers  also  move  more  freely,  being  unencum- 
bered with  extra  armatures  or  other  appliances. 

In  this,  as  in  the  Hicks  repeater,  buttons  are  pro- 
vided, by  means  of  which  each  line  may  be  worked 
separately  without  interfering  with  the  other,  if  desired. 

These  are  omitted  in  the  drawing,  to  prevent  confu- 
sion, but  are  arranged  so  that,  when  closed,  one  button 
forms  a  permanent  connection  between /and  g,  thus 
preventing  the  movement  of  the  lever  I  from  breaking 
the  eastern  main  circuit,  and  another  connects  p  and  /, 
thus  keeping  the  extra  local  circuit  constantly  closed, 
and  the  armature  lever  d'  withdrawn  from  interference 
with  a. 


52 


MODERN  PKACTICE  OF  THE  ELECTRIC   TELEGRAPH. 


The  same  thing  may  be  accomplished  by  causing  the 
button  to  break  the  extra  local  circuit  entirely,  when 
the  instruments  are  to  be  worked  separately,  and  "  turn- 
ing down"  the  adjusting  spring  s'  of  the  lever  d'.  It 
will,  of  course,  be  understood  that  the  other  side  of  the 
repeater  is  arranged  in  precisely  the  same  manner. 


J 


80.  BUNNELL'S  EEPEATER. — The  arrangement  of  the 
main  circuits  in  this  repeater  is  exactly  the  same  as  in 


THE  MORSE,  Oft  AMERICAN  TELEGRAPHIC    SYSTEM  53 

the  ordinary  "button  repeater,'''  and  will  be  readily 
understood  by  reference  to  fig.  29.  The  eastern  main 
wire  enters  at  the  right,  passing  through  the  repeating 
point,  «',  of  the  western  sounder,  S',  and  through  the 
coils  of  the  eastern  relay,  M,  and  thence  to  the  main 
battery  and  earth  at  E.  The  western  main  wire  is 
similarly  connected  on  the  opposite  side  of  the  instru- 
ment. In  the  button  repeater  (75)  a  switch  is  so  ar- 
ranged as  to  form  a  connection,  cutting  out  the  repeat- 
ing points  of  the  sounder  on  the  opposite  side,  when 
either  line  is  working,  requiring  a  person  to  be  con- 
stantly stationed  at  the  instrument  to  make  the  neces- 
sary changes  when  two  stations,  on  opposite  sides  of  the 
repeater,  are  corresponding  with  each  other.  In  Bun- 
nell's  repeater  this  duty  is  performed  automatically  by 
means  of  two  "governor"  or  controlling  magnets,  Gr  Gr, 
the  action  of  which  will  be  hereafter  described. 

The  eastern  and  western  main  circuits  both  being 
closed  and  the  apparatus  at  rest,  the  course  of  the  local 
circuit  of  the  eastern  instrument  is  as  follows  :  From 
the  local  battery,  L,  through  the  coils  of  the  eastern 
sounder,  thence  passing  through  the  closed  relay  points 
at  M,  arid  returning  to  the  other  pole  of  the  battery. 
The  resistance  of  the  governor  magnet,  G,  prevents  any 
appreciable  portion  of  the  current  from  passing  through 
its  coils,  as  long  as  the  closed  points  of  the  relay,  M, 
afford  it  a  shorter  route.  If  the  local  circuit  be  broken 
by  the  relay  points  at  M,  it  is  forced  to  pass  through 
the  coils  of  the  sounder,  S,  and  also  of  the  governor,  G-. 

When  a  circuit  of  low  intensity  passes  through  the 
coils  of  two  magnets,  differing  considerably  in  resistance, 
the  attraction  of  the  magnet  having  the  least  resistance 
is  very  small  in  comparison  with  that  of  the  other.  A 
practical  application  of  this  principle  is  made  in  this  re- 
peater, by  forming  the  helices  of  the  governor  magnet  of 
finer  wire  than  that  of  the  sounders.  The  effect  of  this 
is,  that  when  the  local  circuit  is  thrown  through  both  mag- 
nets by  the  opening  of  the  relay,  that  the  armature  of 
the  governor  magnet  is  attracted  with  considerable 


54  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH* 

strength,  while  the  magnetism  developed  in  the  sounder 
is  not  sufficient  to  move  its  armature,  although  the  same 
current  passes  through  its  coils.  This  arrangement  is, 
of  course,  the  same  on  each  side  of  the  repeater,  and  by 
bearing  it  in  mind  the  action  of  the  instrument  may  be 
readily  comprehended. 

When  both  main  circuits  are  closed  and  the  repeater 
at  rest,  the  governor  magnets  remain  open,  being  cut 
out  by  the  points  of  the  relays,  which,  as  well  as  the 
sounders,  are  closed  on  both  sides  of  the  apparatus.  If, 
now,  we  suppose  the  circuit  to  be  opened  by  an  oper- 
ator on  the  western  main  line,  the  armature  of  the  relay, 
M',  falls  back,  opening  the  sounder,  S',  and  closing  the 
governor  magnet,  G',  as  previously  explained.  This 
breaks  the  eastern  main  circuit  at  s,  and  also  at  a',  as 
well  as  the  circuit  of  the  opposite  governor  magnet,  G, 
at  the  point  b.  The  breaking  of  the  eastern  main  cir- 
cuit at  S'  opens  the  eastern  relay,  M,  and  consequently 
its  sounder,  S,  but  the  circuit  of  the  governor  magnet, 
G,  being  broken  at  5',  it  remains  inactive,  and  the  wes- 
tern main  circuit  is  complete  through  the  points,  a, 
although  broken  at  the  point,  s,  by  the  opening  of  the 
sounder,  S.  Upon  the  closing  of  the  western  main 
circuit  this  action  is  reversed,  and  the  apparatus  re- 
sumes its  original  position.  If  the  eastern  main  circuit 
be  opened  the  same  action  takes  place,  but  on  the 
opposite  side  of  the  repeater. 

In  most  repeaters  hitherto  constructed  one  side  of  the 
apparatus  remains  silent  while  the  opposite  side  is  in 
action,  but  in  this  oire  the  relays  and  sounders  on  both 
sides  work  together,  the  points,  a,  a,  on  the  armature 
of  the  governor  magnets  acting  automatically  in  the 
same  manner  as  the  switch  of  a  button  repeater,  when 
moved  by  the  hand  of  the  operator. 

81.  An  advantage  claimed  for  this  repeater  is,  that 
both  sides  of  the  apparatus  work  together,  affording  the 
operator  in  charge  a  better  opportunity  to  know  how 
both  lines  are  working.  The  extra  local  batteries  are 
dispensed  with,  and  the  relay  levers  are  not  encumbered 


THE  MORSE,  OR  AMERICAN  TELEGRAPHIC  SYSTEM. 


55 


with  extra  armatures  and  other  appliances.  The  ad- 
justments required  are  the  same  as  in  a  simple  relay  and 
sounder. 

82.  Various  other  repeaters  have  been  contrived,  and 
to  some  extent  adopted  in  this  country,  but  as  those  we 
have  described  are  much  more  extensively  used  than 
any  others,  it  has  not  been  deemed  necessary  to  describe 
the  others  in  a  work  of  this  kind. 

83.  COMBINATION  LOCALS. — In   offices   containing   a 
number  of  instruments,  a  single  local  battery  is  fre- 
quently employed  to  operate  all  the  sounders  in  the 
office.     Such  an  arrangement  is  called  a  combination 
local.     The  best  way  of  making  the  connections  is  shown 
in  fig.  30,  in  which  the  instruments  are  represented  at 


I,  II,  III  and  IV.  The  local  battery  is  shown  at  E. 
The  common  conductors,  a  and  b,  should  be  of  large 
copper  wire,  say  No.  1 2  or  14.  If  the  ordinary  Daniell's 
battery  is  used  for  this  purpose,  the  cells  should  be  con- 
nected for  quantity,  as  shown  in  the  diagram,  and  not 
in  a  single  series.  Every  sounder  in  the  combination 
should  have  the  same  size  and  amount  of  wire  in  its 
coils,  as  nearly  as  possible,  in  order  to  secure  the  best 
results. 

84.  Another  plan  is  to  use  separate  locals,  a  wire 
being  run  from  one  pole  of  each  local  to  its  correspon- 
ding instrument,  the  opposite  poles  of  the  batteries,  and 
the  instrument  wires  being  all  connected  to  a  common 
return  wire. 

85.  These  combination  locals  are  very  objectionable, 
however,  and  their  use  should  be  avoided  wherever 


56  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

possible.  The  iron  cores  in  two  different  relays  may 
happen  to  be  in  connection  with  the  silk  covered  wire 
with  which  they  are  wound,  a  circumstance  which  fre- 
quently occurs.  In  such  a  case,  if  the  two  armatures 
chance  to  touch  the  poles  of  their  respective  relays,  a 
metallic  connection,  technically  called  a  cross,  is  made 
between  the  two  main  lines.  Again,  if  these  two  relays 
are  at  a  terminal  station,  and  in  connection  with  two 
main  batteries,  with  opposite  poles  to  the  ground,  the 
combined  force  of  both  batteries  is  thrown  on  short 
circuit,  through  the  local  return  wire,  burning  the  re- 
la}^,  exhausting  the  batteries,  and  interfering  with  the 
operation  of  every  wire  connected  with  them.  The 
cause  of  these  troubles  being  somewhat  obscure,  it  might, 
for  a  considerable  time,  escape  detection. 

86.  LOCAL  CIRCUIT  CHANGER. — In  offices  containing 
two  sets  of  instruments  on  different  circuits,  it  is  often 
desirable  to  change  them.  A  simple  arrangement  for 
this  purpose  it  shown  in  fig.  31,  in  which  the  relays  are 


represented  at  M  and  M' ;  S  and  S'  are  the  sounders  or 
registers,  E  and  E'  are  the  local  batteries.  B  is  a  simple 
button  or  circuit  closer  (62),  having  four  connecting 
points,  1,  2,  3,  4.  When  the  button  is  in  the  position 
1,  2,  as  shown  in  the  figure,  the  relay  M  works  the 
sounder  S,  and  the  relay  M'  the  Sounder  S'.  By 
changing  the  position  of  the  button  to  3,  4,  S  is  worked 
by  M'  and  S'  by  M.  This  simple  arrangement  is  often 
very  convenient  in  railway  stations,  where  a  sounder 
may  be  placed  on  one  circuit  and  a  register  on  the 
other,  so  that  an  operator  who  is  unable  to  read  by 
sound  can  instantly  shift  the  register  upon  either  line 
at  pleasure. 


THE  MORSE,  OR  AMERICAN  TELEGRAPHIC  SYSTEM.  57 

TECHNICAL  TERMS  USED  IN  THE  TELEGRAPH  SERVICE. 

87.  Line. — The  wire  or  wires  connecting  one  station 
with  another. 

Circuit. — The  wires,  instruments,  £c.,  through  which 
the  current  passes  from  one  pole  of  the  battery  to  the 
other. 

Metallic  Circuit. — A  circuit  in  which  a  return  wire  is 
used  in  place  of  the  earth. 

Local  Circuit. — One  which  includes  only  the  appa- 
ratus in.  ah  office,  and  is  closed  by  a  relay. 

Local. — The  battery  of  a  local  circuit. 

Loop. — A  wire  going  out  arid  returning  to  the  same 
point,  as  to  a  branch  office,  and  forming  part  of  a  main 
circuit. 

Binding  Screws  or  Terminals. — Screws  attached  to 
instruments  for  holding  the  connecting  wires. 

To  Cross-connect  Wires. — To  interchange  them  at  an 
intermediate  station,  as  in  §  117. 

To  put  Wires  straight. — To  restore  the  usual  arrange- 
ment of  wires  and  instruments. 

To  Ground  a  Wire,  or  put  on  Ground. — To  make  a 
connection  between  the  line  wire  and  the  earth. 

To  Open  a  Wire. — To  disconnect  it  so  that  no  current 
can  pass. 

Reversed  Batteries. — Two  batteries  in  the  same  cir- 
cuit with  like  poles  towards  each  other. 

To  Reverse  a  Battery. — To  place  its  opposite  pole  to 
the  line  ;  or,  in  other  words,  interchange  the  ground  and 
line  wires  at  the  poles  of  the  battery. 

Escape. — The  leakage  of  current  from  the  line  to  the 
ground,  caused  by  defective  insulation  and  contact  with 
partial  conductors. 

Cross. — A  metallic  connection  between  two  wires, 
arising  from  their  coming  in  contact  with  each  other,  or 
from  other  causes. 

Weather  Cross. — The  leakage  of  current  from  one 
wire  to  another  during  rainy  weather,  owing  to  defec- 
tive insulation. 


CHAPTER  V. 


INSULATION. 


88.  A  telegraph  wire  suspended  on  poles  is  attached 
to  insulators,  to  prevent  the  escape  of  the  current  to  the 
earth  at  the  points  of  support.     Insulators  should  be 
regarded  in  the  light  of  conductors,  whose  value  depends 
,upon  their  resistance  to  the  passage  of  the  current. 

89.  The  insulation  of  a  line  is  never  perfect,  even  in 
the  dryest  weather.     There  is  a  leakage  at  every  sup- 
port, which  is  greatly  increased  when  the  surfaces  of  the 
insulators  are  damp,  especially  if  covered  with  smoke 
or  dirt.     Experiments  show  that  soot  will  destroy  the 
surface  insulation  of  the   best   insulators,   even  when 
exposed  to  the  cleansing  action  of  the  rain.     This  evil 
is  confined,  however,  principally  to  cities,  and  does  not 
manifest  itself  to  nearly  so  great  an  extent  in  the  open 
country. 

90.  Insulators,  considered  as  conductors,  follow  the 
same  law  as  other  conductors.     The  less  the  diameter 
and  the  greater  the  length,  the  more  resistance  is  op- 
posed to  the  escape  of  the  current.     As  in  this  case  the 
resistance  is  almost  entirely  a  question  of  surface,  the 
best  insulator  is  that  having  the  smallest  diameter  and 
the  greatest  length  between  the  wire  and  the  support. 
The  latter  is  accomplished  by  making  the  insulator  of 
a  cup  form,  or  still  better,  of  two  cups,  one  placed 
within  the  other. 

91.  The  material  of  which  the  insulator  is  composed 
shouM  be  a  poor  conductor  of  electricity  and  heat,  a 
non-absorbent  of  moisture,  with  a  surface  repellant  of 
water,  and  free  from  pores  or  cracks.     It  should  also 
remain  unaffected  by  exposure  to  the  weather,  and  the 
effects  of  heat  and  cold.    Nearly  all  of  the  materials 


INSULATION.  |f||  .  fyty 

ordinarily  employed  are,  however,  liable  to  some  of 
these  objections.  „',/. 

Insulators  of  glass  and  porcelain  being  conductors 
of  heat,  a  change  of  temperature  from  cold  to  warm 
causes  a  condensation  of  moisture  upon  their  surfaces, 
including  the  portion  protect- 
ed from  the  direct  action  of 
rain,  and  from  this  arises 
the  principal  objection  to 
the  use  of  these  substances 
in  the  construction  of  an  in- 
sulator. 

Hard  rubber  is  in  itself  •  a 
better  insulator  than  glass  ; 
but  its  surface,  from  exposure 
to  atmospheric  influences,  soon 
loses  its  property  of  repelling 
moisture,  and  becomes  rough 
and  porous. 

A  surface  which  repels  wa- 
tery accumulations  will  cause 
theni:  to  flow  disconnectedly 
in  drops,  instead  of  forming 
a  continuous  conducting  film. 
This  property  is  therefore  one 
of  great  value  for  the  pur- 
poses under  consideration. 

.1 

92.  THE  GLASS  INSULATOR. — The  insulator  most  com- 
monly employed  in  this  country  is  the  glass.  This  is 
generally  made  in  the  form  represented  by  Fig.  32, 
which  is  a  sectional  view  of  the  insulator  fixed  upon  a 
wooden  bracket,  the  latter  being  securely  spiked  to  the 
side  of  the  pole.  The  line  wire  passes  alongside  the 
groove  surrounding  the  insulator,  and  is  fastened  with 
a  tie-wire  encircling  the  insulator,  both  ends  of  which 
are  wrapped  around  the  line  wire.  Tlie  concavity  of 
the  under  side  of  the  glass  keeps  it  dry,  in  some  meas- 
ure preventing  the  current  from  escaping  to  the  wet 


MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 


bracket  and  pole  through  the  medium  of  a  continuous 

stream  of  water. 

93.  THE  WADE  INSULATOR. — This  is  largely  used  in 

the  Western  States.  Its  construction  is  shown  in  Fig.  33. 
A  glass  insulator,  somewhat 
similar  in  shape  to  that  last 
{ described,  is  covered  with  a 
(wooden  shield,  to  prevent  frac- 
ture from  stones  and  other 
causes,  the  wood  being  thor- 
oughly saturated  with  hot  coal 
tar,  to  preserve  it  from  decay. 
The  line  wire  is  tied  to  the 
outside  of  the  shield,  in  the 
same  manner  as  when  the  glass 
insulator  is  used. 

This  insulator  is  usually 
mounted  upon  an  oak  bracket, 
as  in  Fig.  33,  secured  by  spikes 
to  the  side  of  the  pole  or  other 
support.  When  it  is  intended 
to  be  mounted  upon  a  hori- 
zontal cross-arm  it  is  placed 
upon  a  straight  wooden  pin, 
instead  of  a  bracket.  The  pin 
or  bracket  is  usually  saturated 
with  hot  coal  tar,  in  the  same 

manner  as  the  insulator  shield. 


FIG.  34.  Fio.  35. 

94.    FARMER'S    HARD    RUBBER    INSULATOR. — This    is 
shown  in  Fig.  34.     It  is  a  good  insulator  when  new, 


INSULATION. 


61 


but  by  exposure  to  the  weather  its  surface  becomes 
rough  and  spongy,  and  retentive  of  moisture.  It  is 
screwed  to  the  under  side  of  the  cross-arm  or  wooden 
block,  which  is  secured  to  the  pole.  The  best  form  is 
that  which  is  made  with  a  drip  or  shed,  as  shown  in 
the  figure.  If  exposed  to  the  direct  action  of  rain  it 
ought  always  to  be  placed  in  a  perpendicular  position. 
It  will  be  noticed  that  this  insulator  holds  the  line  wire 
by  suspension. 

95.  THE  LEFFERTS  INSULATOR. — This  is  composed  of  a 
suspension  hook  fixed  in  a  socket  of  glass,  of  the  form 
represented  in  Fig.  35.  This  is  inserted  into  a  hole 
bored  in  the  under  side  of  a  block  or  cross-arm,  and 
fastened  with  a  wooden  pin.  In  painting  the  arm  or 
blocks  the  paint  must  not  be  allowed  to  get  on  the  sur- 
face of  the  glass. 


96.  THE  BROOKS  INSULATOR. — Figs.  36  and  37  show 
the  construction  of  this  insulator,  which  consists  of  a 
suspension  hook  cemented  into  an  inverted  blown  glass 
bottle,  which  is  again  cemented  into  a  cast  iron  shell, 
provided  with  an  arm  which  screws  into  the  pole,  as  in 
Fig.  36.  Another  form  is  made,  designed  for  attachment 


62 


MODEKX  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 


to  a  cross-arm,  as  in  Fig.  38.  The  remarkable  insula- 
ting properties  of  this  arrangement  are  mostly  due  to 
the  use  of  paraffine,  with  which  the  cementing  material 
(sulphur)  is  saturated.  It  has  also  been  discovered  that 
blown  glass  possesses  extraordinary  properties  of  repel- 
ling moisture.  Additional  advantage  of  this  fact  has 
been  taken  in  the  construction  of  this  insulator,  as  may 
be  seen  by  reference  to  the  cut. 

97.  Some  important  improvements  have  quite  recently 
been  made  in  the  mechanical  construction  of  the  Brooks 

insulator,  which  are  shown 
in  Fig.  39.  In  the  old 
form  of  hook,  shown  in 
Fig.  37,  the  wire  has  three 
bearings.  To  hold  the 
wire  securely,  it  is  neces- 
sary that  these  bearings 
should  be  so  direct  as  to 
make  it  difficult  to  place 
the  wire  in  it,  and  the 
latter  is  often  weakened 
by  being  bent.  The  new 
hook,  shown  in  Fig.  39, 
has  five  bearings  for  the 
wire,  but  not  so  direct  as 
to  injure  or  weaken  it  by 
bending.  The  wire  can  be 
placed  in  this  hook  without  labor  or  difficulty,  and  a 
strain  cannot  be  applied  in  any  direction  by  means  of 
which  the  wire  can  be  removed  or  released. 

98.  MODE  OF  TESTING  INSULATORS. — The  proper  way 
to  test  the  comparative  value  of  insulators  is  to  fix 
them  upon  frames  or  standards,  in  sets  of  ten  or  more, 
'and  place  them  where  they  will  be  fully  exposed  to 
the   weather.     The   tests   should  be  made   when   the 
weather  is  very  wet,  by  means  of  a  wire  attached  to 
.all  of -them  in  the  usual  manner,   and  leading  to  the 
testing  instrument,  battery  and  ground.    By  this  means 

4he  relative  resistances  of  either  of  the  insulators  above 
described,  and  their  consequent  value  in  the  construc- 
tion of  a  line,  may  be  readily  ascertained. 


FIG.  39. 


INSULATION.  63 

99.  ESCAPE. — When  the  insulation  is  defective,  or  the 
wire  comes  in  contact  with  the  branches  of  trees,  a  wet 
wall,  or  other  partial  conductor,  a  portion  of  the  cur- 
rent passes  to  the  ground,  forming  what  is  technically 
known  as  an  escape. 

100.  WEATHER  CROSS. — The  escape  of  the  current 
from  one  wire  to  another  one  upon  the  same  poles^ 
owing   to  defective   insulation,  is  sometimes  wrongly 
called  "  induction,"  or  "  sympathetic  currents."    Wea- 
ther cross  is  a  much  more  appropriate  term. 

As  electric  currents  always  move  in  the  direction  of 
the  least  resistance,  their  tendency  is  to  escape  from  a 
long  circuit  to  a  shorter  one.  This  mixing  of  the  cur- 
rents from  different  wires  is  a  much  more  serious  evil 
than  a  simple  escape  to  ground,  for  the  latter  may  in 
most  cases  be  overcome  by  increased  battery  power ; 
but  when  cross  connection  exists  between  different 
wires  upon  the  same  poles,  an  increase  of  battery  upon 
one  wire  gives  it  an  advantage  over  the  others,  but 
necessarily  at  their  expense. 

The  effects  of  weather  crosses  usually  manifest 
themselves  upon  the  occurrence  of  a  shower  sooner 
than  the  escape  to  ground,  because  the  horizontal  arms 
become  wet  sooner  than  the  vertical  pole. 

On  the  English  lines  this  difficulty  is  obviated  by 
means  of  an  earth  wire  attached  to  each  pole,  and  wrap- 
ped around  the  center  of  the  arms,  thus  cutting  off  the 
currents  passing  from  wire  to  wire,  and  conveying  them 
to  the  ground.  The  battery  can  then  be  increased  at 
will  on  one  wire,  without  interference  with  the  others. 
A  much  more  economical  and  effective  method  of  obtain- 
ing this  result  is  that  of  improving  the  insulation. 

101.  EFFECT  OF  ESCAPES   AND   GROUNDS   UPON  THE 
CIRCUIT. — If  the  wire  touches  a  conductor  communica- 
ting with  the  earth,  or  the  earth  itself,  in  a  moist  or 
wet  place,  so  that  the  point  of  contact  offers  littl^-or  no 
resistance  compared  with  the  wire  beyond,  the  fault  is 
called  a  ground.     The  effect  of  a  ground  or  escape  is  to 
increase  the  strength  of  the  current  going  out  to  the 


g^  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

line,  and  to  exhaust  the  batteries  more  rapidly.  There- 
fore, in  working  with  a  continuous  current,  as  is  the 
case  on  American  lines,  the  line  current  increases  in 
strength  in  wet  weather,  but  the  variation  or  difference 
in  the  current  at  one  station,  when  the  line  is  opened 
and  closed  at  another,  decreases,  and  the  effective  sig- 
nals are  therefore  weakened. 

102.  THE  LAWS  OF  THE  ELECTRIC  CURRENT. — The 
laws  which  govern  the  propagation  and  distribution  of 
electric  currents  are  so  simple,  and  at  the  same  time  so 
important,  that  every  telegrapher  should  be  familiar 
with  them.  By  their  aid  the  phenomena  above  referred 
to  may  be  readily  comprehended.  The  most  important 
of  these  laws  was  first  enunciated  by  Ohm,  in  1827, 
and  is  known  as  Ohm's  law.  It  may  be  briefly  stated 
as  follows  : 

Call  the  sum  of  the  electro-motive  forces. .  .B 
"  "  internal  resistance  of  the  battery.  .R 
"  "  resistance  of  line  and  instruments.  .L 
"  "  the  effective  strength  of  current. .  .0 

E 


That  is :  The  effective  strength  of  the  electric  current  in 
any  given  circuit  is  equal  to  the  sum  of  the  electro-motive 
forces  divided  by  the  sum  of  the  resistances  (174). 

103.  PRACTICAL  APPLICATION  OF  OHM'S  LAW. — FIRST 
CASE. — To  illustrate  the  application  of  this  law  to  cir- 
cumstances occurring  in  practical  telegraphy,  take  the 


case  of  an  ordinary  telegraph  line  (Fig.  40),  extend- 
ing from  A  to  B,  and  perfectly  insulated,  having  a  re- 
sistance of  100  Ohms.  Let  the  main  batteries,  E  and 
E'  have  each  an  electro-motive  force  of  1,000,  and  a 


INSULATION.  65 

resistance  of  5  ohms,  and  let  the  resistance  of  the  in- 
struments I  and  I'  be  equal  to  10  ohms  each.  The 
total  resistance  of  such  a  circuit  will  be  : 


100  ohms,  line,  I  =  L 

20      "      instruments,  J    ~ 
10      "      batteries,  =  R 

130      "  =  R  +  L 


The  line  being  perfectly  insulated,  the  whole  cur- 
rent from  the  batteries  will  necessarily  act  upon  both 
instruments. 

As  the  effective  strength  of  the  current  in  any  cir- 
cuit is,  by  Ohm's  law,  equal  to  ^^  in  this  case  it  will 
be 

2000 

130    =15'4 
With  key  open  at  A  or  B =  00.0 

Difference,  or  effective  working  strength .  =  15.4 

If,  on  the  above  line,  an  escape  occurs  between  the 
stations  A  and  B,  offering  a  resistance  of -50  ohms,  the 
effect  will  be  the  same  as  if  a  wire  having  a  resistance 
of  50  ohms  were  connected  from  the  centre  of  the  line 
to  the  ground.  The  current  from  each  battery  has  a 
tendency  to  divide  at  the  fault  between  the  two  routes 
open  to  it,  in  proportion  to  their  relative  conductivity; 
or,  what  is  the  same  thing,  in  inverse  ratio  to  their 
respective  resistances.  But  in  this  case  the  electro- 
motive forces  and  the  resistances  are  exactly  the  same 
on  each  side  of  the  fault ;  and  the  positive  current  from 
one  battery,  and  the  negative  from  the  other,  have  an 
equal  tendency  to  escape  to  ground  at  the  fault.  These 
opposite  tendencies  consequently  neutralize  each  other, 
and  no  effect  whatever  is  produced  upon  the  circuit  by 
the  fault  as  long  as  the  line  remains  closed  both  at  A 
and  B. 

If,  however,  A  is  sending  to  B,  his  key  is  alternately 
open  and  closed.  When  open,  the  circuit  of  the  bat* 

I 


(5Q  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

tery  E  (Fig.  41)  is  entirely  broken.  There  will  still, 
however,  be  a  circuit  from  the  battery  E',  through  I1 
and  the  line  to  the  fault  F,  and  thence  to  the  ground. 


[ 
u 

50       » 

EL.. 

I 

By  Ohm's  law  we  find  the  strength  of  this  current  to 
be  as  follows : 

5  ohms  resistance  of  battery,    .     .    =  II 
10      "  "          "  instrument,  ) 

50      "  "          "  i  line,  ]•    =  L 

50      "  "          "  fault, 

115  =  II  +  L. 

C  =    JL 


L          115 

With  the  key  dosed  at  A,  the  strength  of  the  current 
in  the  instrument  at  B  was  found  to  be 

15.4 
With  key  open  at  A,  as  above 8.7 

Difference,  or  effective  working  force. ..     6.7 

In  this  case  the  latter  will  obviously  be  the  same, 
whether  A  sends  to  B  or  B  to  A. 

104.  SECOND  CASE. — Suppose  the  same  fault  to  be 
located  near  A  (see  Fig.  42). 

The  current  from  the  battery  E  will  divide  at  F,  part 
going  to  the  ground  through  the  fault,  and  the  remain- 


der  over  the  line  to  B,  and  through  the  instrument  and 
battery  to  ground.     The  current  from  E'  will  divide  in 


INSULATION.  (J7 

the  same  manner  between  the  fault  and  the  route 
through  I  and  E.  Taking  the  battery  E  alone,  and 
considering  the  other  battery  E'  simply  as  a  conductor, 
the  two  circuits  beyond  the  fault  give  the  following 
resistance  : 

1.  By  the  line  instrument  and  battery  at  B. .   115  ohms.        .-,.£ 

2.  "       faulc  F 50      " 

115    x    50 
Their  joint  resistance  will  be  * —..         r^  =  34.8  ohms. 

Add  resistance  of  battery  itself,  5  ohms,  and  instru- 
ment, I,  10  ohms 15         " 

The  total  resistance  will  be 49. 8 

1000 


This  current  will  divide  at  the  fault  between  the  two 
circuits,  whose  resistances  are  respectively  115  and  50, 
or  in  the  proportion  of  23  to  10.  Therefore  23  parts 
of  the  current  will  go  to  the  ground  at  F,  and  10  parts, 
=  2^2  =  6<1|  wiii  go  over  the  line  to  B. 

The  current  from  the  other  battery,  E',  in  like  man- 
ner divides  at  F,  between  the  fault  and  the  circuit 
through  the  instrument  and  battery  at  A.  The  joint 
resistance  of  the  two  circuits  is 

15    x    50 


Add  the  resistance  of  the  battery  E,  5  ohms,  instrument  I,  10 

ohms,  and  line,  100  ohms  ...........................  .115.0 

Total  resistance  ......................  ..................   126.5 

1000 
The  current  leaving  the  battery  E  will  therefore  be  ,   =       1.9 

The  resistance  of  the  two  circuits  beyond  the  fault 
being  15  and  50,  or  as  3  to  10,  3  parts  will  go  to 
ground  and  10  parts,  or  ^  =6.1,  through  I.  .  /.^ 

*  The  joint  resistance  of  any  two  circuits  is  found  by  dividing  the  product  of  the 
two  resistances  by  their  sum.  When  there  are  three  circuits,  first  find  the  joint  re- 
'sistance  of  two  circuits  as  above,  and  treat  it  as  a  single  circuit,  again  applying  the 
same  rule.  In  the  same  manner  the  joint  resistance  of  any  number  of  circuits  maj 
be  calculated  (175). 


igg  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH, 

When  A  sends  to  B,  the  current  in  the  instrument 
at  B  will  be  : 

Key  closed  at  A. 

From  battery  E' T.9 

«          »   '    E 6.1 

Total  strength  in  I' 14.0 

Key  open  at  A.  ^ 

From  battery  E' -y^r  =  6.1 

«          «       E  ...        0.0       61 


Difference,  or  available  working  current  at  B,  7.9 

Now  let  B  send  to  A.     The  current  at  A  will  be  : 

Key  closed  at  B. 

From  battery  E  .......................  20.0 

••       E'  .  .  .....................     6.1 

Total  strength  in  1  .....................  26.1 

Key  open  at  B. 

1000 
From  battery  E  ...............  —^r~  —  15.4 

"          "       E'  .......................     0.0 

Total  strength  in  1  ...................  15.4 

Difference,  or  available  working  current  at  A,  10.1 


ID     10  10   •  '  ft 


I 

no.  43. 

105.  THIRD  CASE. — Let  the  battery  at  A  be  doubled, 
the  fault  remaining  as  in  the  last  case.  The  electro- 
motive force  and  internal  resistance  of  E  are  both  dou- 
bled, as  in  Fig.  43.  The  current  from  E  will  now  be  : 

,'  '  2000 

50    x    115   =  3G.5 

which  ^vvill  divide  at  the  fault  in  the  same  proportion 
as  before,  the  part  going  to  B  being  3g-58*  10  =  11.0. 

1000 

•     The  current  from  E'  will  be  ilTj>  x  *°  =.7.7,  and  the 
portion  reaching  A  7— -  =  5.5. 


INSULATION.  C9    ' 

"When  A  sends  to  B  the  signals  will  be  as  follows : 

Key  closed  at  A. 

Current  at  B  =  7.7  +  11.0  =  18.7 

Key  open  at  A. 

]000 

Current  at  B =  -T^T-  =     6.1 

loo 

Effective  strength  at  B 12.6 

Now  let  B  send  to  A  : 

Key  closed  at  B. 

Current  at  A  =  36.5  -f  5.5  =  42.0 

Key  open  at  B. 

2000 
(';<j  Current  at  A =  r— -  =  28.6 

Effective  strength  at  A 13.4 

A         E          . 

C: 

FIG.  44. 

106.  FOURTH  CASE. — Double  the  battery  at  B,  the 
fault  remaining  unchanged.     See  Fig.  44. 


Current  from  E  =  50    x    120   _ 

50  +   120  — 

19.9    x    5 
Portion  going  to  B ...    =  • — =     5.8 

2000 


Current  from  E'  =  50x15 

+  50  +   15  ~   15'2 

15.2    x    10 
Portion  going  to  A..    =  ,.. =  11.7 


A  sending  to  B  : 


Key  closed  at  A . 

Current  at  B  =  15.2  +  5.8  =  21.0 

Key  open  at  A. 

2000 
Current  at  B =   -yy^~   =  n-8 

Effective  strength  at  B 9.2 


70  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

B  sending  to  A  : 

Key  closed  at  B. 

Current  at  A  =  19.9  +  11.7  =  31.6 

Key  open  at  B. 

1000 

Current  at  A =  -rr-   =  15.4 

_____ 

Effective  strength  at  A 16.2 

107.  Thus  we  find  that  on  a  circuit  consisting  of 

Line  wire  resistance 100  ohms. 

2  batteries        "        .' 10       " 

2  instruments  "        10       " 

each  battery  having  an  electro-motive  force  of  1000, 
the  signals  received  will  be  as  follows  : 

Signals  at  A.  Signala  at  B. 

When  the  line  is  perfect 15.4  15.4 

With  escape  50  ohms  in  centre 6.7  6.7 

SamefaultatA 10.7  7.9 

Same  fault  at  A,  with  battery  doubled  at  A 13.4  12.6 

Same  fault  at  A,  with  battery  doubled  at  B 16.2  9.2 

108.  The  results  of  this  investigation  may  be  sum- 
med up  as  follows : 

When  the  batteries  and  instruments  are  equal  at 
each  end  of  a  line,  a  given  fault  will  interfere  most 
with  the  working  of  the  circuit  when  in  the  centre. 

When  the  fault  is  near  one  end  of  the  line,  the  sta- 
tion farthest  from  it  will  receive  the  weakest  signals, 
and  the  station  nearest  it  the  strongest  signals. 

In  increasing  the  battery  power  for  working  over  an 
escape,  the  addition  should  be  made  to  the  battery 
nearest  the  fault. 

109.  DISTRIBUTION  OF  BATTERY  POWER. — If  the  in- 
sulation of  a  line  was  perfect  at  all  times,  the  position 
of  the  battery  in  the  circuit  would  be  a  matter  of  .in- 
difference.    As  all  lines,  however,  are  subject  to  more 
or  less  leakage  or  escape  throughout  their  entire  length, 
the  whole  battery  should  not  be  located  at  one  end  of 
a  long  line,  for  in  this  case  signals  would  be  received 
much  better  at  one  end  of  the  line  than  the  other.    The 
usual  arrangement  is  to  place  half  the  battery  at  each 


INSULATION. 


end  of  the  line,  although  if  the  escape  be  uniform 
throughout  the  entire  length  of  the  line,  the  effect  upon 
its  working  will  be  the  same,  whether  all  the  battery 
is  placed  in  the  centre  of  the  line  or  a  portion  of  it  in 
the  centre  and  the  remainder  divided  equally  between 
the  two  ends. 

If  a  certain  portion  of  the  line  is  especially  defective 
in  its  insulation,  the  distribution  of  battery  power  may 
sometimes  be  varied  in  accordance  with  the  principles 
laid  down,  with  manifest  advantage. 

The  insulation  of  the  batteries  themselves  is  a  mat- 
ter of  great  importance,  and  should  never  be  neglected. 
(29.) 

110.  WORKING  SEVERAL  LINES  FROM  ONE  BATTERY.  — 
It  has  been  for  many  years  the  practice  in  this  country 
to  work  a  considerable  number  of  lines  at  the  same 
time  from  a  single  battery.  The  number  of  wires  that 
can  be  worked  in  this  manner  without  interference  de- 
pends entirely  upon  the  proportion  between  the  inter- 
nal resistance  of  the  battery  employed  and  the  joint 
resistance  of  all  the  circuits  connected  with  it.  If  the 
resistance  of  the  battery  itself  is  inappreciably  small 
in  comparison  with  that  of  the  lines  connected  with  it, 
the  current  on  any  given  circuit  will  vary  but  little, 
whether  the  others  be  open  or  closed.  With  the  Grove 
battery  of,  say,  50  cups,  it  is  possible  to  work  as  many 
as  40  or  50  well  insulated  lines,  of  300  miles  or  more 
in  length,  without  appreciable  interference.  The  great 
objection  to  this  system  is  that,  in  wet  weather,  the  re- 
sistance of  the  lines  is  enormously  diminished,  and  the 
interference  of  one  circuit  with  another,  as  a  necessary 
consequence,  greatly  increased. 

It  is  a  common  practice  when  this  occurs  to  increase 
the  number  of  cups  in  the  batter}r,  which  in  most  cases 
has  a  tendency  to  aggravate  the  very  evil  it  is  sought 
to  remedy;  for  with  every  such  addition  the  resistance 
of  the  battery  becomes  greater  in  proportion  to  that  of 
the  lines,  and  the  currents  more  unsteady  and  fluctu- 
ating. No  small  part  of  the  trouble  experienced  in 


f'J  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

working  lines  in  wet  weather  arises  from  this  cause, 
although  usually  attributed  entirely  to  defective  insu- 
lation. It  is  true,  however,  that  the  latter  indirectly 
causes  the  difficulty,  by  lessening  the  resistance  of  the 
wires. 

111.  Experiments  made  on  a  very  wet  day,  upon  a 
number  of  circuits  of  nearly  the  same  length  (100  miles), 
leading  out  of  New  York  city,  proved  that  when  one 
such  wire  was  attached  to  a  carbon  battery  of  60  cups 
the  addition  of  three  other  similar  wires  reduced  the 
current  on  the  first  one  12  per  cent.     It  is  a  common 
practice  to  attach  as  many  as  eight  wires  to  such  a  bat- 
tery, which  in  the  above  case  would  have  reduced  the 
current  about  25  per  cent. 

112.  It  is  the  opinion  of  many  scientific  experts  in 
practical  telegraphy  that  increased  efficiency,  as  well  as 
economy,  would   result  from  working  telegraph  lines 
with  a  single  series  of  Daniell's  battery,  in  its  most  ap- 
proved form,  upon  each  circuit.     The  objection  urged 
against  this  battery  is  the  increased  amount  of  room  it 
takes  up,  as  well  as  its  somewhat  greater  original  cost. 

113.  As  long  as  the  present  system  remains  in  vogue, 
care  ought  to  be  taken  that  the  different  circuits  leading 
from  the  same  battery  are  as  nearly  as  possible  equal 
in  resistance ;  and  it  must  not  be  forgotten  that  the  in- 
terference caused  by  attaching  too  many  wires  to  a 
battery  cannot  le  remedied  by  the  addition  of  more  cups 
for  intensity.     The  electro-motive  force  of  a  carbon  bat- 
tery is  exhausted  with  a  rapidity  nearly  in  proportion 
to  the  number  of  circuits  supplied  from  it.     In  the  case 
of  the  Grove  battery  this  effect  is  not  so  apparent. 


CHAPTER   VI. 


TESTING    TELEGRAPH   LINES. 

1  114.  Interruption  and  interferences  from  various  causes 
are  constantly  occurring  upon  telegraph  lines,  and  one 
of  the  most  important  of  an  operator's  duties  is  to  be 
able  to  discover  promptly  the  nature  and  location  of  a 
fault,  that  measures  may  immediately  be  taken  for  its 
removal.  This  is  done  by  an  investigation  called  test- 
ing. The  apparatus  and  methods  now  in  general  use 
in  this  country  are  of  a  somewhat  primitive  nature,  but 
the  improved  modes  of  testing  which  have  long  been 
employed  in  Europe  are  gradually  becoming  appreci- 
ated here,  and  as  these  are  based  on  sound  scientific 
principles,  it  is  to  be  hoped  that  they  will  soon  super- 
sede the  imperfect  ones  heretofore  employed. 

115.  The  principal  interruptions  to  which  a  telegra- 
phic circuit  are  liable  may  be  summed  up  as  follows : 

DISCONNECTION. — The  continuity  of  the  circuit  is 
broken,  so  that  no  current  passes  over  the  line.  . 

PARTIAL  DISCONNECTION. — This  is  usually  caused  by 
rusty  and  unsoldered  joints  in  the  line,  or  by  loose 
screw  connections  in  offices  or  about  switches,  which 
offer  great  resistance  to  the  passage  of  the  current. 

ESCAPE  or  leakage  of  current  from  the  line  to  the 
ground,  caused  by  defective  insulation,  or  contact  with 
trees,  &c.  When  an  escape  is  sufficient  to  entirely 
prevent  the  working  of  the  line  it  is  called  a  "ground." 

CROSS. — When  two  wires  are  in  contact,  so  that  one 
cannot  be  worked  without  interfering  with  the  other. 

WEATHER  CROSS. — When  a  portion  of  the  current 
from  one  wire  leaks  into  others  upon  the  same  poles, 
through  defective  insulation.  The  effect  is  similar  to 
that  of  a  cross,  but  much  less  strongly  marked.  This 
is  often  improperly  called  sympathy,  or  induction. 


Y4  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

DEFECTIVE  GROUND  CONNECTION. — It  sometimes  Lap- 
pens  that  the  ground  wire,  or  ground  plate,  at  a  termi- 
nal station,  is  defective.  The  effect  of  this  is  to  make 
the  wires  connected  with  it  appear  as  if  in  contact,  or 
crossed.  This  difficulty  is  often  caused  by  the  removal 
of  a  meter  in  offices  where  a  gas  pipe  is  used  as  a 
ground  connection  for  several  lines. 

116.  TESTING  FOR  DISCONNECTION. — If  the  circuit  is 
broken  at  any  point  the  relays  will  all  remain  open. 
The  operator  at  each  way  station  should  immediately 
proceed  to  test  the  wire  by  connecting  his  ground  wire, 
first  on  one  side  of  the  instruments  and  then  on  the 
other.  If  either  connection  closes  the  line  circuit,  the 
interruption  is  on  that  side,  as  the  circuit  of  the  oppo- 
site main  battery  is  completed  through  the  ground,  in 
place  of  the  broken  wire.  If  the  ground  wire  gives  no 
circuit  either  way,  it  is  probable  that  the  interruption 
is  in  the  office,  or  that  the  ground  connection  is  defec- 
tive. Each  operator  should  always  first  make  sure 
that  the  fault  is  not  in  or  about  his  own  office.  Having 
ascertained  the  direction  in  which  the  difficulty  lies,  he 
should  at  once  report  the  state  of  the  case  to  the  ter- 
minal station  at  the  opposite  end. 


FIQ.  45. 

Fig.  45  represents  a  line  with  four  stations,  A.  B,  C 
and  D.  Suppose  the  wire  broken  at  F.  By  connect- 
ing the  ground  wires  at  B  and  C,  as  shown,  two  dis- 
tinct circuits  are  formed.  A  can  work  with  B,  and  C 
with  D,  showing  that  the  fault  is  between  B  and  C. 

Disconnection  is  usually  caused  by  the  breaking  of 
the  line  wire,  or  by  a  key  carelessly  left  open.  Some 
other  causes  are  wires  loose  in  their  binding  screws,  or 
defective  switches,  or  the  fine  wire  in  or  about  the  re- 


TESTING    TELEGRAPH   LINES.  ^5 

lay  may  be  broken.     The  latter  is  sometimes  burned 
in  two  by  atmospheric  electricity. 

317.  PARTIAL  DISCONNECTION. — It  is  rather  difficult 
to  discover  this  fault  by  the  ordinary  relay  tests.  It  is 
frequently  of  an  intermittent  character,  and  requires  to 
be  very  carefully  tested  for.  In  the  latter  case,  the 
best  plan  is  to  cross  connect,  or  interchange  the  defec- 
tive wire  with  a  good  one  at  the  terminal,  and  also  one 
other  station,  as  in  Fig.  46.  Suppose  the  fault  is  at  F,  on 
No.  2  wire  ;  by  cross  connecting  at  A  and  B,  as  shown, 


FIG.  4G. 

the  fault  will  shift  to  No.  1  circuit,  showing  that  it  is 
between  those  points.  If  it  were  beyond  B,  it  would 
remain  on  No.  2  circuit.  In  this  case,  let  the  wires  be 
put  straight  at  B,  and  cross  connected  at  C,  and  so  on, 
station  by  station.  When  the  fault  is  passed  it  shifts  to 
the  other  circuit,  and  will  therefore  be  found  between 
the  two  last  stations. 

118.  To  TEST  FOR  AN  ESCAPE. — Call  the  stations  up 
in  rotation,  beginning  with  the  one  farthest  off,  and 
have  them  open  key  for  a  minute  or  two.  When  a 
station  beyond  the  escape  is  open,  more  or  less  current 
will  still  pass  out  to  the  line  through  the  relay,  return- 
ing through  the  ground  from  the  fault. 


£ 


Suppose  A  (Fig.  47)  is  testing.  When  the  circuit  is 
open  at  C  or  D  a  current  will  pass  from  E  through  the 
fault,  F,  which  will  be  interrupted  when  B  opens,  show- 
ing the  fault  is  between  B  and  C. 


70  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

119.  TESTING  FOR  GROUNDS. — A  ground  is  tested 
for  in  a  similar  manner.  The  operator  at  a  way  sta- 
tion can  ascertain  which  side  of  him  the  ground  is 
situated,  from  the  fact  that  it  cuts  off  or  greatly  weak- 
ens the  main  battery  current  from  that  direction,  when 
tested  with  a  ground  wire  by  means  of  the  finger  or 
tongue. 

Telegraph  lines  are  very  liable  to  be  grounded  by 
the  action  of  atmospheric  electricity  upon  the  lightning- 
arresters.  These  should  be  carefully  looked  after  at 
frequent  intervals,  especially  where  exposed  to  damp- 
ness, as  in  cable  boxes. 

]  20.  TESTING  FOR  CROSSES. — In  case  a  cross  is  sus- 
pected between  two  wires,  say  Nos.  1  and  2,  instruct 
the  most  distant  station  to  open  one  wire,  preferably 
the  through  wire,  or  No.  1,  and  "send  dots"  upon  the 
other.  Open  No.  2  at  your  own  station,  and  if  the  dots 
sent  on  No.  2  at  the  distant  station  are  received  on 
No.  1,  the  wires  are  crossed.  Care  must,  of  course,  be 
taken  not  to  be  deceived  by  the  leakage  from  one  wire 
to  another,  caused  by  defective  insulation.  If  the 
wires  are  in  actual  contact,  the  signals  received  upon 
No.  2  wire  will  be  nearly  or  quite  as  strong  as  if  re- 
ceived upon  No.  1. 

Next,  instruct  the  distant  station  to  leave  No.  1  open, 
and  open  it  also  at  your  own  station.  No.  2  will  now 
be  free  from  interference,  and  the  stations  upon  it  may 
be  signalled  without  difficulty.  Call  them  in  regular 
succession,  commencing  at  the  farthest  end  01  the  line, 
and  instruct  each  one  in  turn  to  send  dots  on  No.  2.  If 
the  dots  are  received  on  both  wires  the  cross  is  be- 
tween you  and  the  station  sending ;  but  if  upon  No.  2 
only,  it  is  beyond  that  station.  It  is  better  that  each 
operator,  while  sending  dots,  should  open  the  other 
wire,  if  practicable. 

The  principle  of  this  test  will  be  understood  by  refer- 
ence to  Figs.  48  and  49,  which  represent  a  two  wire 
line,  with  four  stations,  A,  B,  C  and  D,  the  wires  being 
"  crossed"  between  B  and  C.  The  operator  testing  for 


TB3T1XO   TELEGRAPH   UNES. 


the  cross  is  supposed  to  be  at  A.  In  Fig.  48  station  C 
has  No.  1  open,  and  station  A  has  No.  2  open.  If  C 
sends  dots  on  No.  2  the  circuit  will  shift  to  No.  1,  at 
the  cross,  as  shown  by  the  arrows,  and  the  dots  will 


come  on  No.  1  instrument  at  A,  showing  that  the  cross 
is  between  A  and  C.  In  case  C  were  unable  to  open 
No.  1  the  effect  would  evidently  be  the  same,  provided 
it  remains  open  at  D. 

Now  let  C  close  both  wires,  and  B  open  No.  1,  and 
write  dots  on  2  (Fig.  49).  If  No.  2  be  open  at  A,  B 
will  be  unable  to  work  in  this  case,  as  both  wires  are 
open,  one  at  A  and  the  other  at  B.  With  both  wires 


closed  at  A,  B's  dots  will  come  on  No.  2,  the  current 
from  F  passing  over  both  wires  to  the  cross,  and  from 
thence  on  No.  2,  No:  1  being  open,  as  shown  in  the 
figure.  Thus  the  fault  is  located  between  B  and  C. 

In  large  offices,  where  there  are  a  considerable  num- 
ber of  wires,  it  will  often  be  found  a  much  more  con- 
venient and  expeditious  method  of  testing  for  crosses 
for  the  operator  to  station  himself  at  the  switch  with  a 
single  instrument,  which  can  be  placed  at  pleasure  on 
any  wire,  for  the  purpose  of  communicating  with  differ- 
ent stations.  When  any  station  is  "  sending  dots  "  the 
testing  operator  can  feel  them  by  placing  a  linger  upon 
the  ground  wire,  and  another  upon  the  proper  line  wire 


V8' 


MODERN  PRACTICE  OF  TIIS  ELECTRIC  TELEGRAPH. 


at  the  switch.  The  principle  involved  is  of  course  the 
same  as  in  the  method  first  described.  In  wet  weather, 
however,  testing  by  the  sense  of  feeling  is  attended 
with  much  uncertainty,  as  it  is  impossible  to  distinguish 
between  the  effect  of  a  metallic  cross,  or  actual  contact, 
and  the  leakage  arising  from  bad  insulation. 

121.  It  would  be  difficult  to  specify  all  the  minor  in- 
terruptions that  are  liable  to  occur  in  and  about  tele- 
graph offices,  or  on  the  lines  ;  the  operator  will  there- 
fore, in  many  cases,  be  obliged  to  depend  upon  his  own 
ingenuity  for  the  best  method  of  testing  applicable  to 
each  particular  case.     By  carefully  studying,  however, 
the  principles  heretofore  explained,  the  intelligent  tele- 
grapher will  usually  be  able  to  cope  with  any  difficulty 
that  may  chance  to  arise  in  the  ordinary  service  of  the 
lines. 

122.  TESTING  WITH  THE  GALVANOMETER   AND  RE- 
SISTANCE COILS. — In  the  more  accurate  and  scientific 
modes  of  testing,  which  have  been  for  some  years  em- 


LINE 


ployed  upon  the  European  lines,  the  instruments  used 
are  the  differential  galvanometer  and  a  set  of  standard 
resistance  coils  (44). 

The  arrangement  of  the  connections  will  be  under- 
stood by  reference  to  Fig.  50. 


TESTING    TELEQRAPH    LINES.  *^9 

The  galvanometer  coils  are  wound  with  two  wires  of 
the  same  length  and  resistance,  insulated  from  each 
other  with  the  utmost  care.  The  needle  is,  therefore, 
surrounded  by  an  equal  number  of  convolutions  of  each 
wire,  which  are  also  equi-distant  from  it. 

The  inner  end  of  one  coil  surrounding  the  galvano- 
meter, g,  is  joined  to  the  outer  end  of  the  other  at  a, 
and  a  key,  K,  attached  to  this  junction,  when  de- 
pressed, forms  the  connection  with  the  testing  battery, 
E.  The  other  ends  of  the  coils  run  to  binding  screws, 
M  M',  for  the  convenient  attachment  of  lines  to  be 
tested.  The  principle  upon  which  the  action  of  the 
instrument  depends  is  the  following : 

When  the  battery  is  connected  by  depressing  the 
key  the  current  divides  into  two  equal  portions  at  a, 
one  flowing  from  a  to  M,  tending  to  deflect  the  needle 
to  the  left,  and  the  other  from  a  to  M',  tending  to  de- 
flect it  to  the  right;  but  as  long  as  the  two  currents  are 
of  the  same  strength  they  balance  each  other,  and  the 
needle  remains  at  rest.  Suppose  that  the  terminal  M' 
is  connected  to  a  telegraph  line  whose  remote  end  is  to 
ground,  and  the  terminal  M  is  connected  through  the 
resistance  coils,  R,  to  the  ground  likewise,  as  shown  in 
Fig.  50.  We  have  already  seen  (102)  that  the  strength 
of  an  electric  current  is  in  all  cases  equal  to  the  electro- 
motive force  divided  by  the  resistance.  Therefore,  if 
in  this  case  we  let 

E  =  electro-motive  force  of  battery, 

I  —  resistance  of  line  wire, 

g  =  resistance  of  galvanometer  coil, 

r  =  resistance  coils  in  circuit, 

the  current  in  the  two  circuits  surrounding  the  needle 
will  be 

E  E 

y—  «*   — r 

If,  therefore,  the  resistance  coils  in  circuit  be  varied 
until  r  =  /,  the  needle  will  remain  unaffected.  As  the 
earth  offers  no  appreciable  resistance  to  the  passage  of 
the  current,  the  resistance  of  the  line  I  will  be  accu- 


gO'  MODERN  PRACTICE  OF  THK  ELECTRIC  TELEGRAPH. 

rately  represented  by  the  amount  of  resistance  inter- 
posed at  r,  in  order  to  bring  the  needle  to  zero.  The 
value  of  the  above  equation  will  obviously  not  be 
affected  by  any  change  in  the  value  of  E. 

123.  The  resistance  coils,  R;:accompanying  the  gal- 
vanometer, are  so  arranged  asjto  be  adjustable  to  any 
required   resistance,  from  1  ojim  up  to  10,000.     For 
the  measurement  of  still  higher  resistances  one  coil  of 
the  galvanometer  is  provided  with  three  "  shunts,"  or 
branch  circuits,  x,  y,  z,  having  resistances  respectively 
equal  to  £,  JVt  and  ^;  therefore,  if  x  be   connected, 
TV  of  the  current  will  pass  through  g,  and  /o  through 
the  shunt.     In  the  same  manner  y  and  z  respectively 
allow  but  Tw  and  ToVo-  of  the  current  to  pass  through 
one  wire  of  the  galvanometer,  when  connected,  and  by 
this  means  the  instrument  maybe  made  to  measure 
any  resistance,  from  0.001  up  to  10,000,000  ohms. 

124.  TESTING  FOR  THE  DISTANCE  OF  FAULTS. — The 
principle  upon  which  the  methods  of  distance  testing  are 
founded  is  that  of  finding  the  resistance  of  the  line  wire 
between  the  testing  station  and  the  fault  by  means  of 
the  apparatus  described.     When  the  line  is  broken  at 
any  point  one   of  the   following  four  cases  generally 
occurs  : 

1.  Line   wire   broken,   giving   full,    or   nearly  full, 
ground  connection. 

2.  Line   wire   unbroken,  but   gives   nearly   enough 
escape  to  ground  to  make  signals  imperceptible. 

3.  Line  wire  broken,  without  making  contact  with 
earth. 

4.  A  cross  between  two  wires,  so  that  signals  sent 
on  one  are  communicated  to  both. 

125.  It  is  very  essential  that  the  resistance  of  each 
circuit  should  be  frequently  measured  and  recorded,  so 
that  when  a  fault  occurs  the  actual  resistance  per  mile 
of  the  line  may  be  known.     If  the  broken  line  gives  a 
full  ground,  its  resistance  divided  by  the  resistance  per 
mile  at  once  gives  the  distance  of  the  break  from  the 
testing  station  •  and  if  the  distant  station   obtains  a 


TESTING   TELEGRAPH    LINES.  31 

corresponding  result,  the  confirmation  is  complete. 
Thus,  in  a  line  of  100  miles  in  length,  if  the  tests  from 
the  two  extremities  indicate  distances  of  45  and  55 
miles,  respectively,  the  locality  of  the  interruption  is 
clearly  indicated.  As  the  fault,  however,  usually  gives 
a  very  considerable  resistance  at  the  point  where  the 
line  is  in  contact  with  the  earth,  and  the  sum  of  the 
two  resistances,  measured  from  stations  at  the  opposite 
ends  of  the  line,  greatly  exceeds  the  resistance  of  the 
line  itself  when  perfect,  it  is  usual  in  such  cases  to 
estimate  the  fault  midway  between  the  two  points  indi- 
cated. Thus,  when  the  respective  resistances  indicate 
86  and  26  miles,  the  sum  of  these  exceeds  100  miles  by 
12,  and  therefore  half  this  excess,  or  6,  is  deducted 
from  each  of  the  measures. 

126.  When  the  line  is  unbroken,  but  shows  a  heavy 
escape  or  partial  ground,  sufficient  to  weaken  signals, 
two  or  three  different  methods  are  available  for  deter- 
mining  its   locality.     The  first  plan  is  that  of  direct 
measurement,  alternately  from  each  end,   the  distant 
end  at  the   same   time   being  insulated,  or,  in  other 
words,  left  open,  in  the  manner  explained  in  the  last 
paragraph.     In  this  case  the  resistance  of  the  fault  is' 
measured  twice  over,  and  is  roughly  allowed  for  by  the 
method  of  calculation  above  given. 

127.  THE  LOOP  TEST. — A  second  and  more  accurate 
method,  which  gives  a  measure  entirely  independent  of 
the  resistance  of  the  fault  itself,  is  known  as  the  loop 
test.     It   is  only  available,  however,  in   cases  where 
there  are  two  or  more  parallel  wires  on  the  same  route. 
In  order  to  make  this  test,  let  the  operator  proceed  as 
follows  : 

Make  the  length  to  be  tested  as  short  as  possible, 
and  have  all  the  instruments  in  circuit  taken  out.  Se- 
lect a  good  wire,  similar,  if  possible,  to  the  one  it  is 
required  to  test.  Both  these  wires  must  then  be  con- 
nected together  in  a  loop,  at  the  nearest  available  sta- 
tion beyond  the  fault,  without  ground  connection.  The 
resistance  of  the  faulty  wire,  when  perfect,  must  be 


82 


MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 


ascertained.   This  may  be  taken  from  previous  records,, 
or  it  may  be  found  thus  : 


^--Sr       M       GOOD   WIRE 


Connect  one  end  of  the  'loop  to  the  +  pole  of  the 
battery  E,  and  the  other  to  one  of  the  galvanometer 
wires  at  M'.  Connect  also  the  +  pole  of  the  battery 
with  the  resistance  coils,  R,  at  N,  and  the  —  pole  of 
the  battery  to  the  key,  K,  and  common  terminal,  a,  of 
the  galvanometer.  Connect  the  remaining  galvanome- 
ter wire  with  the  resistance  coils  at  M  (Fig.  51). 


Having  ascertained  the  resistance  of  the  loop,  ar- 
range the  connections  as  shown  in  Fig.  52. 

Upon  depressing  the  key,  K,  the  battery  current  will 


TESTING   TELEGRAPH    LINES. 

'  ] 

flow  through  M  and  R,  and  also  through  the  loop.  The 
resistance  required  at  R  to  balance  the  needle  will  be 
equal  to  the  sum  of  the  resistance  of  the  two  linesj 
Although  there  is  a  partial  ground  at  F  it  will  not 
affect  the  measurement,  as  there  is  no  other  ground  in 
circuit. 

Connect  the  +  pole  of  the  battery  E  to  ground,  and 
connect  the  —  pole  to  the  key  K.  Connect  the  perfect 
wire  of  the  loop  to  one  of  the  galvanometer  wires  at  M\ 
and  the  faulty  wire  to  the  other  galvanometer  wire  at 
M,  interposing  the  resistance  coils  R.  When  the  key 
K  is  depressed  the  current  from  the  battery  E  flows" 
into  both  lines  simultaneously,  passing  to  the  ground 
through  the  fault  at  F.  By  adding  resistance  at  R,  so 
as  to  bring  the  needle  to  zero,  the  resistance  a  1ST  F 
will  be  made  equal  to  a  M'  F. 

The  resistance  thus  added,  deducted  from  the  total1 
resistance  of  the  loop,  previously  ascertained,  and  di- 
vided by  two,  is  the  resistance  of  the  line  between  N 
and  F. 

Thus,  if  the  resistance  of  the  loop  be  1,000  ohms, 
and  100  ohms  have  been  added  to  the  defective  wire  to 
balance  the  needle — 

Then  M0>)  ~  10°  —  450  ohms,  the  resistance  of  the  wire 
between  the  resistance  coils  R  and  the  fault. 

Let  M'  F  =  a,  N  F  =  y. 

Then  x  +  y  =  L,  the  resistance  of  the  loop. 

As  R  +  y  =  x,  or  R  +  N  F  =  M'  P. 

L  — R 
Therefore,  y  =  — - — 

Suppose  that  the  loop  of  1,000  ohms  measures  120 
miles,  then,  by  proportion, 

If  1,000  ohms  =  120  miles,  450  ohms  =  64  miles. 

When  an  instrument  or  section  of  small  wire  is  in- 
cluded in  the  circuit,  allowance  must  be  made  for  their 
resistance.  It  is  a  great  assistance  in  these  tests  to, 
know  from  previous  records  the  exact  resistance  oi 
every  section  of  the  line. 


g£  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

-  128.  BL  AVI  ER'S  FORMULA  FOR  LOCATING  AN  ESCAPE.— • 
Where  there  is  but  one  wire  the  following  method  may 
be  employed.  Three  tests  have  to  be  taken  for  the 
operation,  viz : 

« ;.  *  ,     Let  R  =  resistance  of  the  line  before  it  was  defective.    This  must 

be  obtained  from  previous  records. 
(  "    S  =  resistance  of  the  line  when  grounded  at  the  distant  end. 

"   T  =  resistance  of  the  line  when  disconnected  at  the  distant  end. 

Multiply  S  by  S  and  T  by  E,  and  add  the  products 
together;  subtract  from  this  amount  T  times  S,  and 
also  R  times  S.  Subtract  the  square  root  of  the  re- 
mainder from  S  ;  the  remainder  will  give  the  resistance, 
x,  or  the  distance  of  the  fault  from  the  testing  station. 

.This  process  appears  complicated,  but  is  in  reality 
very  simple.  For  example,  suppose  the  line  100  units 
loner,  and  the  fault  68  units  distant,  and  the  resistance 
of  tli2  fault  9G  units,  as  shown  in  Fig.  53 

X 68  V32 


Then  R       =:       x  +  y        =         63  +  32       =       100 

.s  =;.;£.  =M+»_£«=   92 

T       =       x  +  z          =         68  +  96       =       164 

We  shall,  however,  have  obtained  these  resistances 
by  measurement,  and  not  by  calculation.  We  there- 
fore have  : 

S  x  S  =  92  x   92  =  8464 )  , .  ' 
T  x  R  =  164  x  100  =  16400  J 

T  x  S  =  164  x   92  =  15088  )  24288 
R  x  S  =  100  x   92  =  9200  J  ~ ^fg 

And  the  square  root  of  576  is  24;  which  deducted,  S  = 
92,  gives  68  as  the  resistance  of  x,  or  the  distance  of 
the  fault  from  the  testing  station. 

The  distance,  cc,  being  known,  the  others  are  obtained 
with  ease ;  for  R  —  68  gives  y,  the  distance  from  the 
opposite  end ;  and  T  —  68  gives  2,  or  the  resistance  of 
the  fault  itself.  This  test  should  be  taken  from  both 

*  See  note,  §  104, 


TESTING    TELEGRAPH   LINES.  g 

ends  of  the  line,  if  possible.  In  the  above  calculation 
the  resistance  of  the  fault  is  supposed  to  remain  con- 
stant during  the  measurements  ;  but  as  this  is  not  often 
the  case  in  practice,  the  average  of  several  measure- 
ments should  be  taken. 

129.  To  FIND  THE  DISTANCE  OF  A  CROSS. — The  two 
wires  in  contact  form  a  loop,  provided  they  are  clean, 
and  are  twisted  together,  so  that  the  contact  offers  no 
appreciable  resistance.  In  such  a  case  open  both  wires, 
at  the  nearest  station  beyond,  and  test  the  resistance  of 
the  loop.  Half  this  resistance  will  be  the  resistance  of 
the  wire  between  the  galvanometer  and  the  fault,  and 
from  this  the  distance  can  be  calculated,  as  before  ex- 
plained (127).  All  relays  in  circuit  must  be  taken  out, 
or  the  proper  allowance  made  for  their  resistance. 

As  it  is  difficult  to  tell  with  certainty  whether  the 
cross  offers  resistance  or  not,  it  is  a  better  plan  to  test 
it  as  a  ground.  Test  each  wire  in  turn  by  the  loop 
method  (127),  grounding  the  wire  at  both  ends.  The 
wire  tested  will  then  make  a  ground  through  the  other 
wire  at  the  point  of  contact,  and  the  location  of  the 
latter  may  be  readily  ascertained. 

Second  Method* — Suppose  two  wires.  A  and  B,; 
touch  one  another  at  the  point  F.  Connect  A  to  the 
zinc  of  the  testing  battery,  leaving  it  open  at  the  re- 
mote end  ;  it  will  then  serve  as  a  battery  wire  between 
the  battery  and  the  fault  (F).  Ground  B  at  the  distant 
end,  and  connect  it  to  one  coil  of  the  differential  gal- 
vanometer at  the  testing  station  Put  the  other  wire 
of  the  galvanometer  to  ground.  The  current  of  the 
battery  will  pass  along  the  wire  A  and  "divide  at  F, 
one  portion  going  to  ground  at  the  distant  end  of  B, 
and  reaching  the  galvanometer  through  the  wire  con- 
nected with  the  ground,  the  other  portion  returning  to 
the  galvanometer  through  the  nearer  portion  of  B.  If 
the  cross  is  exactly  in  the  centre  of  B  the  needle  will 
not  move,  as  the  two  currents  will  balance  each  other, 

If  one  section  of  B  is  longer  than  the  other,  the  resist^ 

_ , * 

*  Culley's  Handbook,  3d  edition,  page  279. 


g£  MODERX  PRACTICK  OF  THE  ELECTRIC  TELEGRAPH. 

ance  added  to  the  shorter  section  to  balance  the  needle 
will  show  the  difference  in  the  resistance  of  the  two 
sections. 

Let  L  =  the  total  resistance  of  B. 
"  x  =  resistance  of  the  shorter  portion. 
(i  L  —  x  =  "          "       longer        " 
1  R  =  resistance  added  to  shorter  portion. 

L-R 
Then  x  =  — ^ — 

.  130.  ADVANTAGES  OF  TESTING  BY  MEASUREMENT. — 
The  testing  of  lines  by  actual  measurement  lies  at  the 
very  foundation  of  all  efforts  to  improve  the  working 
of  our  telegraphic  system.  The  insulation  resistance  of 
each  of  the  principal  circuits  should  be  measured  every 
morning,  and  a  record  of  the  results  kept  for  reference. 
In  England  the  standard  of  insulation  is  1,000, 000  ohms 
per  mile  in  the  worst  of  weather.  Therefore,  a  line 
of  200  miles  should  not  give  less  than  ±~^  =  5,000 
ohms.  If  it  gives  less  than  this  the  low  resistance  is 
due  to  defective  insulation.  The  line  should,  in  that 
case,  be  tested  in  many  separate  sections,  either  from 
the  terminal  office  or  by  a  visit  to  each  section.  If  the 
resistance  per  mile  is  the  same  for  each  section,  the 
fault  is  probably  owing  to  the  nature  of  the  insulation; 
but  if,  as  is  usually  the  case,  some  sections  are  very 
much  worse  than  others,  the  trouble  will  be  found  in 
contact  with  trees,  broken  insulators,  and  the  like.  A 
visit  to  the  faulty  locality  will  disclose  the  cause  of  tho 
evil. 

131.  In  comparing  the  insulation  of  line  wires  of 
different  lengths,  the  insulation  per  mile  must  be  ascer- 
tained, othel-wise  the  longest  wire  will  appear  the 
worst;  therefore,  multiply  the  insulation  test  in  ohms 
by  the  length  of  the  wire  in  miles.  If  the  insulation  is 
uniformly  good  throughout  the  circuit  tested,  the  leak- 
age will  increase  in  direct  proportion  to  the  length  of 
the  wire,  irrespective  of  its  thickness  or  conducting 
power,  for  the  resistance  of  the  wire  is  very  small  in 
comparison  with  the  insulators,  and  need  not  be  taken 
into  account. 


TESTING    TELEGRAPH    LINES.  $•[ 

The  following  example  from  Culley's  work  will  illus- 
trate this.  The  figures  given  are  the  result^  of  an  ae- 
tual  test : 

The  wire  A  had  a  leakage  equal  to 29 

"         B      "          "  "      30 

"         C      "         "  "      50 

Total  leakage. . .  : 109 

The  three  wires,  when  connected  together  at  the  test- 
ing end  and  left  open  at  the  distant  end,  gave  a  com- 
bined leakage  of  110. 

When  connected  so  as  to  form  a  continuous  wire,  open 
at  the  distant  end,  the  leakage  was  still  110.  The  ex- 
periment was  repeated,  and  extended  to  other  wires, 
with  the  same  result.  In  this  case  the  resistance  of  the- 
insulators  was  very  great  compared  with  that  of  the 
wire — as  much  as  t^o  million  ohms  per  mile.  But  on 
a  wet  day  three  similar  wires,  whose  respective  leak- 
ages were  196,  185  and  141,  making  a  total  of  552, 
when  looped  in  a  continuous  line,  as  in  the  second  case 
above,  gave  a  test  of  only  476,  the  distant  portion  of 
the  wire  being  in  reality  tested  by  a  current  weakened 
by  the  leakage  in  the  nearer  portions. 

132.  TESTING  FOR  CONDUCTIVITY  RESISTANCE. — The 
metallic  resistance  of  the  line  wires  should  be  occasion- 
ally tested  in  sections,  in  the  finest  weather.  The  re- 
sistance should  be  uniformly  in  proportion  to  the  length 
of  the  wire.  If  any  section  discloses  an  unusually  high 
resistance  per  mile,  it  is  very  probable  that  there  are 
rusty,  unsoldered  joints  in  the  line,  or  that  the  ground 
connections  are  defective.  It  is  difficult  for  those  who 
have  not  tried  it  to  believe  the  vast  improvement  that 
may  be  made  in  any  line  in  a  few  days  by  actual  mea- 
surement, and  an  inspection  of  the  sections  which  give 
indications  of  being  defective. 

It  is  not  an  uncommon  occurrence  to  find  that  a  single 
unsoldered  joint  in  galvanized  iron  wire,  which  appears 
perfectly  firm  and  sound,  will  give  a  resistance,  when 
tested  by  the  galvanometer,  equal  to  many  miles  of 
line.  A  line  containing  many  bad  joints  will  frequently 


88 


MODERX  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 


work  better  in  wet  than  in  dry  weather,  as  the  mois- 
ture increases  the  conductivity  of  the  oxide  between 
the  wires  at  the  joints. 

In  testing  for  conductivity,  with  the  distant  end  of 
the  wire  to  ground,  as  in  Fig.  54,  the  result  is  some- 
times interfered  with  by  earth  currents.  It  is  there- 
fore better,  when  practicable,  to  use  the  loop  method, 
by  connecting  the  wire  to  be  measured  in  a  loop  with 
another  wire  of  known  resistance.  Unless  this  test  is 
made  in  fine  weather,  however,  the  leakage  from  one 
wire  to  the  other  will  decrease  the  resistance  of  the 
loop.  The  battery  must  also  be  insulated  from  the 


LINE: 


CD J3 

FIG.  54. 

earth,  otherwise  the  leakage  at  each  insulator  will  de- 
crease the  apparent  resistance,  especially  if  the  insula- 
tion is  defective.  For  instance,  two  wires  on  the  same 
poles,  disconnected  and  looped  at  the  distant  end,  had 
a  resistance  of  6,475  ohms  when  the  battery  was  en-? 
tirely  disconnected  from  the  earth.  Upon  putting  the 
zinc  pole  of  the  battery  and  the  line  attached  to  it  to 
earth,  the  apparent  resistance  fell  to  5,250  ohms.  The 
insulation  resistance,  with  one  wire  disconnected,  was 
9,250  ohms,  the  weather  being  damp. 


CHAPTER   YII. 


NOTES    ON   TELEGRAPHIC   CONSTRUCTION1. 

133.  In  order  to  maintain  uninterrupted  telegraphic 
communication  between  any  two  points,  it  is  of  the  first 
importance  that  the  line  should  be  well  constructed  and 
properly   insulated   throughout.     There  are  numerous 
minor  details  in  the  construction  and  repairing  of  tele- 
graph lines  which  merit  much  more  attention  than  they 
generally  receive.     The  bad  working  of  our  lines  is  in 
a  great  measure  owing  to  the  neglect  of  these  appa- 
rently trifling  details,  through  ignorance  or  carelessness. 

134.  POLES. — The   poles   intended   for  an  ordinary 
line  should  never  be  less  than  five  inches  in  diameter 
at  the  top,  their  length  depending  upon  the  number  of 
wires  to  be  provided  for,  and  in  some  measure  upon 
the  location  of  the  line.     They  should  be  set  in  the 
ground  to  the  depth  of  five  feet,  wherever  practicable. 

In  setting  poles  around  the  curve  of  a  railway,  they 
should  be  made  to  lean  back  against  the  strain  of  the 
curve. 

135.  WIRE. — For    ordinary  lines,   galvanized    iron 
wire,  of  No.  8  or  9,  Birmingham  gauge,  is  generally 
employed.     For  short  lines,  No.  10  or  11  will  answer 
very  well.     The  "American  Compound  Wire,"  a  re- 
cent invention,  is  composed  of  a  combination  of  a  steel 
core  with  a  sheathing  of  copper.     It  has  come  into  ex- 
tensive use  within  the  short  time  which  has  elapsed 
since  its  introduction,  and  has,  thus  far,  been  found  to 
answer  admirably.     A  wire  of  this  kind,  having  a  con- 
ductivity equal  to  a  No.  8  iron  wire,  weighs  but  112 
pounds  per  mile. 

136.  The  less  the  size,  and  consequently  the  conduc- 
tivity of  the  line  wire,  the  more  care  is  required  in  its 


90  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

insulation,  for  an  increased  resistance  virtually  adds  to 
the  length  of  the  circuit.  Increased  conductivity  thus  ad- 
mits of  a  reduction  in  battery  power,  with  a  consequent 
decrease  in  the  escape  of  electricity,  and  long  circuits 
may  be  thus  worked  with  much  greater  facility;  a  fact 
which  has  been  most  unaccountably  ignored  in  the  con- 
struction of  the  greater  portion  of  the  lines  in  this 
country. 

137.  GALVANIZED    OR    ZINC    COATED    WIRE    must 
always  be  used  for  permanent  work,  for  rust  reduces 
the  conducting  power  of  wires  very  rapidly.     This  is 
especially  the  case  with  the  smaller  sizes,  such  as  No. 
11  or  12.     In  smoky  places  it  is  a  good  plan  to  paint 
the  wire  before  it  is  put  up,  for  the  gas  arising  from  the 
combustion  of  coal  destroys  the  zinc  coating  in  a  short 
time,  as  may  be  observed  in  many  of  our  larger  cities. 

138.  ARRANGEMENT   OF   WIRES   UPON  THE  POLE. — 
Wires  arranged  vertically  upon  the  poles,  or  one  above 
another,  are  more  liable  to  get  into  contact  with  each 
other  than  when  arranged  horizontally  upon  cross-arms. 
When  placed  one  above   another,  each  alternate  wire 
should  be  fastened  upon  opposite  sides  of  the  poles. 

It  is  better  not  to  place  wires  of  different  sizes  upon 
the  same  poles  or  cross-arms  if  it  can  be  avoided,  as 
they  are  much  more  likely  to  get  "  crossed"  than  wires 
of  the  same  size  would  be,  as  they  do  not  keep  time 
with  each  other  when  swung  to  and  fro  by  the  wind. 

139.  JOINTS  OR  SPLICES. — In   the   construction  of  a 
line  nothing  is  of  greater  importance  than  the  perfect 
continuity  of  the  circuit,  and  this  depends,  in  a  great 
measure,  upon  the  perfection  of  the  joints.     The  impor- 
tance of  this  has  been  very  generally  overlooked  by 
the  telegraphers  of  this  country,  and  much  trouble  in 
working  lines  has  been  experienced  in  consequence,  the 
cause  of  which  has  remained  unsuspected.     A  single 
rusty  unsoldered  joint  will  often  cause  more  resistance 
than  fifty  miles  of  line. 

No  joint  or  splice,  however  clean  and  firm,  can  be 
depended  upon  if  made  by  mere  contact  or  twisting. 


NOTES  ON  TELEGRAPHIC  CONSTRUCTION.  0 

Sooner  or  later  the  metals  will  certainly  rust,  and  this 
tendency  is  increased  by  the  passage  of  the  current. 
When  copper  and  iron  wires  are  joined  together  the 
joint  is  especially  liable  to  become  defective  from  this 
cause.  It  is  a  common  error  to  suppose  that  joints 
made  in  galvanized  wire  do  not  require  soldering. 

140.  In  making  a  joint  each  wire  should  be  twisted 
round  the  other,  in  the  manner  represented  in  Fig.  55, 
the  turns  passing  as  close,  and  as  nearly  at  right  angles 
as  possible  to  the  wire  which  they  surround.  A  wire 
must  never  be  spliced  by  being  bent  back  and  twisted 
around  itself. 


141.  The  best  solution  for  soldering  is  chloride  of 
zinc,  with  a  little  muriatic  acid  added,  for  the  purpose 
of  cleansing  the  wire.     In  connecting  copper  and  iron 
wire  together,  it  is  well  to  wash  off  the  chloride  of  zinc, 
and  then  coat  the  joint  with  paint  or  rosin,  or  else  to 
solder  with  the  rosin  alone.     This  will  prevent  local 
galvanic  action  between  the  metals. 

142.  FIXING  THE  INSULATORS. — In  attaching  insula- 
tors to  the  poles  they  should  be  arranged  in  such  a 
manner  as  to  prevent,  as  far  as  possible,  the  lodgment 
of  snow  about  them,  so  as  to  form  an  escape  between 
the  wire  and  its  support.    The  glass  insulator  is  usually 
cemented  to  the  bracket  by  means  of  white  lead  or 
asphaltum.     The  edge  of  the  insulator  must  never  le  per- 
mitted to  touch  the  shoulder  of  the  bracket;  for  in  this  case, 
during  a  shower,  a  continuous  stream  of  water  flows 
directly  from  the  wire  to  the  pole,  entirely  destroying 
the  usefulness  of  the  insulator.     For  the  same  reason 
an   insulator   ought  never  to  be  fastened  down  to  a 
bracket  by  means  of  a  spike  driven  over  it,  as  is  often 
done  where  there  is  an  upward  strain  upon  the  wire. 
,The  proper  way,  in  such  cases,  is  to  use  some  form  of 


92  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

"hook,  or  suspension  insulator,  and  fasten  the  line  into 
it  with  a  tie-wire. 

In  turning  a  sharp  angle  it  is  better  to  put  on  two 
insulators  and  brackets  at  the  corner  pole,  or  the  wire 
will  be  liable  to  come  in  contact  with  it. 

When  the  Lefferts  or  Brooks  insulator  is  used,  there 
is  danger  of  fracturing  the  glass  while  stringing  wire, 
by  violently  wrenching  the  wire  into  the  hooks.  By  a 
little  precaution  this  result  may  be  avoided. 

143.  Insulators  and  brackets  are  sometimes  attached 
to  a  cross-arm,  or  other  support,  in  a  horizontal  posi- 
tion.    This  ought  never  to  be  allowed,  for  a  driving 
rain  will  wet  the  whole  inner  surface  of  the  insulator, 
causing  a  great  leakage  of  the  current  at  every  sup- 
port.    The  same  thing  often  occurs  with  improperly 
shaped  brackets,   which  cause  the  spray  from  falling 
rain-drops  to  be  dashed  against  the  inside  of  the  insu- 
lator.    The  shoulder  of  the  bracket  ought  to  be  rounded 
or  sloped  off,  so  as  to  prevent  this  from  happening. 

Unless  the  insulator  is  securely  fastened  to  the  pin 
or  bracket  which  supports  it,  it  is  liable  to  be  lifted  off 
by  the  wind,  causing  an  interruption. 

144.  LEADING  WIRES  INTO  OFFICES. — The  wires  lead- 
ing into  offices  are  fruitful  sources  of  escapes  and  other 
interruptions,  as  the  work  is  often  very  unskilfully  or 
carelessly  done.     Gutta-percha  covered  wires,  unless 
well  protected,  become  entirely  useless  in  a  year  or 
two,  if  exposed  to  the  air  and  light.     The  method  em- 
ployed in  England  to  protect  this  kind   of  wire  might 
be  adopted  with  great  advantage  in  this  country.     The 
gutta-percha  wire  is  first  covered  with  tape,  and  then 
saturated  with  a  preservative  mixture.* 

The  best  way  to  lead  wires  through  the  side  of  a 
building  is  to  enclose  them  in  hard  rubber  tubes,  with 

*  This  mixture  is  made  and  applied  as  f  >llows:  Take  equal  portions  of  wood  tar, 
gas  tar  and  slacked  Mme.  Boil  tfiese  together,  stirring;  them  well  while  boiling,  until 
the  moisture  is  entirely  driven  out,  which  may  be  known  by  the  subsidence  of  the 
frothing.  When  cool  apply  to  the  taped  wire,  and  then  cover  the  latter  with  dry 
sand.  ITang  the  wire  up  to  dry  in  the  air,  and  in  three  or  four  days  it  will  be 
ready  for  use.  This  coating  resists  sun  and  moisture,  and  effectually  protects  th« 
gutta-percha. 


NOTES    ON   TELEGRAPHIC    CONSTRUCTION.  Q3 

the  outer  ends  inclined  downwards,  to  prevent  moisture 
from  entering.  In  arranging  these  wires,  it  should  be 
borne  in  mind  that  the  current  will  follow  moisture  and 
dampness  along  the  outer  surface  of  covered  wire, 
unless  it  is  so  placed  that  the  line  of  leakage  is  broken 
at  some  point. 

145.  FITTING  UP  OFFICES. — In  running  wires  inside 
an  office,  it  is  better  never  to  allow  two  wires  to  touch 
each  other,  even  when  covered  with  an  insulating  coat- 
ing, as  this  may  be  burned  by  lightning  or  otherwise 
rendered  imperfect    causing  a  cross-connection.     The 
proper  mode  of  arranging  the  office  connections  and 
running  the  wires  to  the  instruments  is  shown  in  Figs. 
17  and  18,  pages  34  and  35.    Splices  in  the  office  wires 
should  be  avoided  as  far  as  possible,  but  when  required, 
they  should  be  made  by  turning  each  wire  eight  or  ten 
times   around  the   other.      A   less   number   of    turns 
answers  for  the  line  wire,  because  the  strain  tends  to 
keep  the  joint  pressed  together.     Great  care  must  be 
observed  in  making  the  joint  between  the  iron  and  cop- 
per wire,  which  must  in  all  cases  be  soldered. 

146.  GROUND    CONNECTIONS. — It   is   of  the   utmost 
importance  that  the  ground  plate  at  each  end  of  the 
line  should  make  a  perfect  connection  with  the  earth. 
The  plate  must  be  large,  and  buried  deep  in  wet  soil 
below  the  reach  of  frost.     A  water  or  gas  pipe  makes 
an   excellent  ground   connection.      The   ground   wire 
should   be  attached  outside  the  metre,  as  the  latter 
is  liable  to  be  occasionally  disconnected  for  repairs.     It 
is  advisable,  whenever  practicable,  to  form  a  connection 
both  with  the  gas  and  water  pipes.     The  connection 
should  be  carefully  made  and  always  well  soldered. 

147.  CABLES. — The  shore  ends  of  cables  should  be 
bedded  well  out  to  low  water  mark.     Dig  the  trench 
to  a  good  depth,  and  cover  the  cable  with  a  piece  of 
heavy  plank  or  joist,  and  secure  it  well  with  heavy 
stones,  laid   at  short  intervals.    -If  the   covering   be 
merely  of  sand  it  will  soon  wash  away  and  leave  the 
cable  uncovered.     Newer  allow  any  portion  of  a  calk  to 


94 


MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 


le  exposed  to  sun  or  air,  but  cover  it  all  the  way  from 
the  box  where  the  connection  is  made  with  the  air  line. 

Cable  boxes  always  ought  to  be  made  double  (one  box 
within  another),  in  order  to  prevent  wet  from  entering. 
The  unskilful  manner  in  which  these  are  often  arranged 
is  a  fruitful  source  of  trouble  in  working  lines. 

Lightning  arresters  should  be  kept  attached  to  cables 
all  the  year  round.  It  is  not  uncommon  for  heavy  light- 
ning to  occur  in  midwinter  in  this  country. 

148.  MAKING  JOINTS  IN  CABLES. — In  splicing  cables, 
or  other  gutta-percha  wire,  the  following  is  the  method 
recommended  by  the  Bishop  Gutta-Percha  Company, 
who  have  manufactured  the  greater  portion  of  the  sub- 
marine cables  in  use  in  this  country  : 

"  Use  gutta-percha  one  sixteenth  of  an  inch  thick,  cut 
in  pieces  to  suit  the  joint.  Soften  it  in  hot  water,  and 
keep  it  flat  Wipe  the  surface  with  a  cloth.  Heat  the 
surface  by  holding  it  near  a  flat  file  or  other  iron,  about 
as  hot  as  a  laundress's  iron  ;  if  the  iron  causes  the 
gutta-percha  to  smoke,  it  is  too  hot.  When  dry  and  a 
little  sticky,  wind  two  or  three  coatings  of  gutta-percha 
around  the  joint,  taking  care  that  each  coating  is  per- 
fect and  each  layer  is  dry ;  then  smooth  off  and  lap 
the  joint  well  over  on  the  gutta-percha  on  each  side  of 
the  joining.  Use  no  spirit  lamp,  nor  anything  with  a 
Haze.  When  gutta-percha  is  burned  it  cannot  be  re- 
stored. Hot  water  joints  are  worthless.  They  will  not 
stand,  and  will  open  when  dried  out. 

"In  making  joints  it  is  absolutely  necessary  that  the 
hands  of  the  operator  should  be  clean,  and  that  no 
water,  grease,  dirt,  or  anything  of  the  sort  must  be 
allowed  to  touch  the  gutta-percha." 

149.  Another  method  is  given  in  Culley's  Handbook 
of  Practical  Telegraphy,  as  follows  : 

"Prior  to  making  the  joint  the  gutta-percha  is 
removed  from  the  ends  of  the  wires  for  about  one  and 
a  half  inches,  and  the  copper  wires  are  carefully  cleaned 
by  scraping;  the  wires  are  twisted  together  for  one 
inch,  the  sharp  ends  being  closely  trimmed  off.  The 


NOTES    ON    TELEGRAPHIC    CONSTRUCTION.  95 

joint  is  then  soldered  with  rosin  and  good  soft  solder, 
containing  a  sufficiency  of  tin. 

"After  this  the  gutta-percha  is  scraped,  or  very 
carefully  pared  back  for  about  two  inches,  to  remove 
its  outer  surface,  which  is  oxidized,  and  will  not  join 
properly  ;  the  wire  joint  is  covered  with  Chatterton's 
compound*  and  the  gutta-percha,  heated  on  both  sides, 
and  tapered  down  over  the  joint  till  that  from  each  side 
meets.  The  junction  is  completed  by  means  of  a  warm 
joining  tool,  care  being  taken  to  mix  the  gutta-percha 
well  without  burning.  As  soon  as  this  has  cooled  an- 
other coating  of  Chatterton's  compound  is  spread  over 
the  gutta-percha,  taking  care  not  to  burn  the  compound. 

"A  new  and  clean  sheet  of  gutta-percha  is  then 
heated  by  means  of  a  spirit  lamp,  and  while  so  heated 
carefully  stretched  so  as  slightly  to  thin  it.  Then, 
while  it  and  the  Chatterton  coated  joint  are  still  hot,  it 
is  laid  on  the  joint,  and  pinched  tightly  round  it  with 
the  finger  and  thumb,  after  which  it  is  trimmed  off  close 
with  scissors.  The  seam  is  again  pinched  and  carefully 
finished  off  with  a  warm  tool,  so  as  to  mix  the  gutta- 
percha  of  the  two  sides,  and  the  coating  of  the  wire 
itself,  well  together. 

"The  joint,  when  cool,  is  again  covered  with  Chat- 
terton's compound,  and  a  longer  and  larger  sheet  of 
gutta-percha  is  laid  over  it,  pinched,  cut,  and  tooled  off 
as  before. 

"When  the  joint  is  complete,  another  coating  of 
Chatterton's  compound  is  applied  over  the  whole,  well 
tooled  over  the  joint,  and  when  cool,  rubbed  with  the 
hand,  well  moistened,  till  the  surface  is  smooth. 

"The  mixing  of  the  old  and  the  new  gutta-percha 
is  most  important,  and  joints  generally  fail  from  this 
having  been  imperfectly  done,  or  from  the  percha  being 
overheated.  Cleanliness  is  essential  to  success.  The 
fingers  should  be  used  as  little  as  possible,  and  must  be 
kept  very  clean." 

*  The  ingredients  of  this  are  by  weight,  as  follows'  one  part  of  Stockholm  tar; 
one  part  of  rosin,  and  three  parts  of  gutta-percha. 


CHAPTER   Till. 


HINTS     TO     LEARNERS. 

150.  FORMATION    OF   THE   MORSE    ALPHABET. — The 
characters  of  the  American  Morse  Alphabet  are  formed 
of  three  simple  elementary  signals,  called  the  dot,  the 
short  dash  and  the  long  dash,  separated  by  variable 
intervals  or  spaces.     There  are  four  spaces  employed  in 
this  alphabet,  viz.,  the  space  ordinarily  used  to  sepa- 
rate the  elements  of  a  letter ;    the  space  employed  in 
what  are  termed  the  "spaced  letters,"  which  will  be 
hereafter  referred  to  ;  the  space  separating  the  letters  of 
a  word;  and  lastly,  that  separating  the  words  them- 
selves. 

The  value  of  these  spaces  should  be  carefully  im- 
pressed upon  the  mind  of  the  learner.  Beginners  are 
apt  to  conceive  that  the  Morse  alphabet  consists  solely 
of  dots  and  dashes,  and  this  misconception  has  a  ten- 
dency to  greatly  increase  the  time  required  to  become 
good  "senders."  Uniformity  and  accuracy  in  spacing 
is  of  no  less  importance  than  in  the  formation  of  the 
letters  themselves.  The  foundation  of  perfect  Morse 
sending  lies  in  the  accurate  division  of  time  into  mul- 
tiples of  some  arbitrary  unit. 

151.  The  duration  of  a  dot  is  the  unit  of  length  in 
this  alphabet. 

1.  The  short  dash  is  equal  to  three  dots. 

2.  The  long  dash  is  equal  to  six  dots. 

3.  The  ordinary  space  between  the  elements  of  a  let- 
ter is  equal  to  one  dot. 

4.  The  space  employed  in  the    "spaced  letters"  is 
equal  to  two  dots. 

5.  The  space  between  the  letters  of  a  word  is  equal 
to  three  dots. 

6.  The  space  between  two  words  is  equal  to  six  dots. 


HINTS   TO    LEARNERS.  97 

The  dot  is  an  unfortunate  appellation  for  this  sign, 
because  it  conveys  the  idea  of  a  point,  or  to  speak  elec- 
trically, a  current  of  infinitely  short  duration.  Elec- 
tro-magnets, however,  require  time  in  magnetization 
(38).  Currents  involve  time  in  transmitting  signals. 
Clock-work  requires  time  to  run.  Currents  must  be  of 
sensible  duration.  The  dot,  therefore,  involves  time, 
but  this  time  is  variable,  according  to  circumstances. 
The  length  of  the  dot  should  increase  with  the  length 
of  the  circuit.  In  long  submarine  lines  the  dot  has  to 
be  made  longer  than  the  dash  itself  on  short  open  air 
lines,  and  the  same  thing  occurs  in  working  through 
repeaters  (76).  In  commencing,  therefore,  the  habit 
should  be  acquired  of  making  short,  firm  dashes,  instead 
of  light,  quick  dots.  After  the  student  has  once  learned 
to  send  well,  it  is  very  easy  to  learn  to  send  fast,  but 
after  once  getting  in  the  habit  of  sending  short  and 
rapid  dots,  or  ''clipping,"  it  is  almost  impossible  to 
get  in  the  way  of  sending  firmly  and  steadily.  Begin- 
ners should  rather  take  pride  in  the  accuracy  with 
which  they  space  out  the  elements  of  the  telegraphic 
music  than  in  the  number  of  words  they  can  stumble 
through  in  a  minute. 

152.  In  the  excellent  little  Manual  of  Prof.  Smith* 
six  elementary  principles  are  laid  down  as  the  basis 
for  practicing  the  alphabet,  viz  : 

First  principle.     Dots  close  together.  >^ 
I  S  HP  6 


Second  principle.     Dashes  close  together. 
M  5  T 

Third  principle.     Lone  dots,      j  *~ 
E 

Fourth  principle.     Lone  dashes.         ^_ 
T        L  or  cipher 

*  Published  by  L.  G.  Tillotson  &  Co.,  New  York 
7 


f)g  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

Fifth  principle.     A  dot  followed  by  a  dash. 
A. 

Sixth  principle.     A  dash  followed  by  a  dot. 

N 

153.  Correctness  in  sending  depends  in  a  great  mea- 
sure upon  the  manner  in  which  the  key  itself  is  handled. 
Place  the  first  two  fingers  upon  the  top  of  the  button 
of  the  key,  with  the  thumb  partly  beneath  it,  the  wrist 
being  entirely  free  from  the  table.     The  motion  should 
be  made  by  the  hand  and  wrist,  the  thumb  and  fingers 
being  employed  merely  to  grasp  the  key.     The  motion, 
both  up  and  down,  must  be  free  but  firm.     Tapping 
upon  the  key  must  be  strenuously  avoided.. 

154.  The  downward  movement  of  the  key  produces 
dots  and  dashes ;  the  upward  movement  spaces.     It  is 
first  necessary  to  acquire  the  habit  of  making  dots  with 
regularity  and  precision,  then  dashes,  and  finally  com- 
binations of  dots  and  dashes.     It  is  the  best  plan  for 
the  student  to  practice  upon  a  register  in  a  local  circuit 
with  his  key,  as  he  will  the  more  readily  be  able  to 
observe  and  correct  the  faults  in  his  manipulation. 

155.  The  student  may  now  proceed  to  practice  upon 
the  elementary  principles. 

1.  Practice  making  dots  at  regular  intervals,  until 
they  are  produced  with  the  regularity  of  clock-work, 
and  of  definite  and  uniform  dimensions.     The  regular 
tick  of  a  watch  or  of  a  short  pendulum  is  a  valuable 
auxiliary  in  acquiring  this  habit. 

2.  Next  proceed  to  make  dashes,  first  at  the  rate  of 
about  one  per  second  of  time,  which  may  afterwards  be 
slowly  increased   to   three.     The   space   between   the 
dashes  must  be  made  as  short  as  possible.     If  the  up- 
ward motion  of  the  hand,  in  forming  the  space,  be  made 
full,  it  cannot  be  made  too  quick. 

3.  The  third  principle  occurs  but  once  in  the  alpha- 
bet, and  forms  the  letter  E.     It  is  made  by  a  quick  but 
firm  downward  movement  of  the  key.     In  practicing 


HINTS   TO   LEARNERS.  <}<) 

upon  this  or  any  other  character,  it  should  not  be 
repeated  too  rapidly,  nor  should  the  thumb  and  fingers 
be  taken  from  the  key  in  the  intervals  between  the  suc- 
cessive repetitions  of  the  letter. 

4.  The  fourth  principle  is  somewhat  difficult.     The 
usual  tendency  is  to  make  T  too  long  and  L  too  short. 
It  will  be  observed  that  the  same  character  is  used  for 
L  and  the  cipher  or  0.     Occurring  by  itself  or  among 
letters  it  is  always  translated  as  L,  but  when  found 
among  figures  becomes  0.     This  would  at  first  seem 
liable  to  cause  confusion,  but  in  practice  it  is  found  not 
to  be  the  case.     It  was  formerly  the  custom  to  make 
the  cipher  equal  to  three  short  dashes. 

5.  The  fifth  principle,  which  forms  the  letter  A,  may 
be   timed   by  the   pronunciation   of  the   word   again, 
strongly  accenting  the  second  syllable.     The  tendency 
of  beginners  is  usually  to  make  the  dot  too  long  and 
the  dash  too  short,  and  more  especially  to  separate 
them  too  much. 

6.  The  final  principle,  the  dash  followed  by  a  dot, 
usually  presents  some  difficulties.     The  universal  ten- 
dency of  the  student  is  to  separate  the  dot  from  the 
dash  by  too  great  a  space.     Time  the  movement  by 
pronouncing   the   word  ninety,  with  the  first  syllable 
somewhat  longer  than  usual. 

156.  Having  become  thoroughly  conversant  with  the 
six  elementary  principles,  the  following  exercises  may 
be  taken  up  in  order. 

(1.)     E        I        S        H  P  6 

These  should  be  practiced  separately,  until  the  right 
number  of  dots  can  be  made  invariably,  the  last  dot  in 
each  being  neither  shorter  nor  longer  than  the  prece- 
ding ones. 

(2.)          T        M  5  Tf         L  or  cipher. 

In  practicing  this  exercise,  care  must  be  taken  not 
to  separate  the  dashes  too  much,  and  to  make  the  final 
one  in  each  letter  exactly  equal  to  the  preceding  ones. 


1'0()  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 

Observe  not  to  make  the  L  too  short.  There  is  a  gen- 
eral tendency  in  beginners  to  shorten  the  final  dash, 
where  two  or  more  occur  together. 

(3.)         A  U  Y  4 

The  usual  tendency  to  make  too  much  space  between 
the  dot  and  dash,  in  the  above  letters,  may  be  avoided 
by  making  them  as  if  by  prolonging  the  final  dot  in  I, 
S,  H  and  P. 

(4.)  I  A  S  U 

H  V  P"          T 

These  are  to  be  practiced  in  couples,  as  represented, 
the  object  being  to  impress  upon  the  student  the  differ- 
ence in  the  characters  thus  coupled  together. 

(5.)      N  p  B  _  8 

The  student  having  thoroughly  mastered  the  sixth 
elementary  principle,  he  will  have  no  difficulty  in  form- 
ing the  above  characters. 

(6.)         AFX  Parenthesis 

Comma        Semicolon         "W  1 

.  The  only  caution  necessary  in  this  exercise  is  to  form 
the  letters  compactly,  with  the  dashes  of  equal  length. 
(See  Exercise  2.)  Observe,  that  the  Parenthesis  may 
be  formed  by  running  A  U  together,  and  the  Semicolon 
by  AF,  etc. 

(7.)      U  Q  2  Period  3 

These  differ  but  little  from  exercises  previously  prac- 
ticed, and  require  no  particular  directions. 

(8.)     K  J  9  Interrogation 

G  7  Exclamation 

J  and  K  are  generally  considered  the  most  difficult 
letters  in  the  alphabet.  Do  not  separate  J  into  double: 


HINTS    TO    LEARNERS.  101 

N,  and  be  careful  that  the  dashes  correspond  in  length. 
(See  Exercise  2.)  The  figures  7  and  9  require  care  in 
spacing  correctly. 

(9.)  0  R  &  C  Z  Y 

These  are  termed  the  "spaced  letters,"  and  require 
great  care  in  order  to  make  them  correct!}'.  The 
"space"  should  be  just  double  that  ordinarily  used 
between  the  elements  of  a  letter.  The  usual  tendency 
is  to  make  it  too  great.  It  should  be  just  sufficient  t6 
distinguish  these  characters  from  I,  S  and  H. 

157.  The  construction  and  manipulation  of  the  alpha- 
bet having  been  thoroughly  mastered  by  the  practice 
of  the  foregoing  exercises,  it  is  now  presented  in  its 
complete  and  consecutive  form. 

I.  ALPHABET. 

A  ~  0  -- 

B  — -  P  

C  -.  Q  

D  —  R  ... 

E  -  S  ... 

F  —  T  _ 

G  U  — 

H  ....  Y  -— 

I  -  W  

J  X  

K  Y  .... 

L  —  Z  .... 

M  —  &  .... 

N  —  , 

II.  NUMERALS. 


1  . 6  —. 

2  7  — 

3  8  — 

4  9  — 

5 0  — 


102  MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH, 


III.    PUNCTUATION,  ETC. 

*Period  Exclamation  . 

Comma  fParenthesis  

Semicolon  Italics  

Interrogation  ^Paragraph  — — 

Numbers  are  always  sent  twice  over,  to  avoid  error ; 
once  written  out  in  full,  and  then  in  figures.  In  frac- 
tions one  dot  is  used  to  represent  the  line  between  the 
numerator  and  denominator. 

158.  It  is   necessary  to   again  caution  the  student 
against  falling  into  the  common  error — from  which  most 
books  on  the  telegraph  are  not  exempt — that  is  enter- 
tained respecting  the  elementary  signs  of  the  Morse 
alphabet.     It  is  said  to  consist  of  two  characters,  the 
dot  and   the   dash.     The   importance  of  the  space  is 
utterly  ignored.     The  difference  between  good  and  bad 
sending  is  almost  entirely  a  matter  of  spacing.     A  com- 
mon fault  of  young  operators  is  to  run  their  words  too 
closely  together. 

If  the  principles  laid  down  in  this  work  be  firmly 
adhered  to,  the  learner  will  be  surprised,  not  only  at 
the  rapidity  with  which  he  masters  what  appears  to  be 
a  very  difficult  lesson,  but  at  the  extreme  accuracy  with 
which  he  manipulates  his  instrument.  He  must  also 
carefully  bear  in  mind  that  one  of  the  most  universal 
faults,  among  those  attempting  to  learn  the  telegraphic 
art,  is  that  of  going  over  a  great  deal  and  learning 
nothing  well. 

159.  READING  BY  SOUND. — This  can  only  be  attained 
by  constant  and  persevering  practice,  keeping  in  mind 
the  principles  above  given.     The  lever  of  the  Morse 
apparatus  makes  a  sound  at  each  movement,  the  down- 

*  The  Semicolon,  Parenthesis  and  Italics  are  seldom  used  in  this  country.  It  is 
customary  among  operators  to  ejnphasize  particular  words  by  separating  the  letters 
more  widely  than  ordinarily. 

|  Preceding  and  following  the  words  to  which  they  refer. 

$  When  this  occurs  the  copyist  makes  a  new  paragraph,  b/  commencing  the 
next  word  upon  another  line. 


HINTS   TO   LEARNERS.  103 

ward  motion  producing  the  heavier  one,  or  that  repre- 
senting clots  and  dashes  ;  or,  more  properly,  the  heavy 
stroke  indicates  the  commencement  of  a  dot  or  dash 
and  the  lighter  one  its  cessation.  A  dot  makes  as  much 
noise  as  a  dash,  the  only  difference  being  in  the  length 
of  time  between  the  two  sounds.  Thus,  if  the  recoil  or 
lighter  stroke  be  dispensed  with,  it  would  be  impossible 
to  distinguish  E,  T  and  L  from  each  other. 

In  learning  to  read  by  sound  it  is  best  for  two  per- 
sons to  practice  together,  taking  turns  at  reading  or 
writing,  and  each  correcting  the  faults  of  the  other. 
The  characters  must  first  be  learned  separately,  and 
then  short  words  chosen  and  written  very  distinctly  and 
well  spaced,  the  speed  of  manipulation  being  gradually 
increased  as  the  student  becomes  more  proficient  in 
reading.  After  becoming  sufficiently  well  versed  in  the 
art  to  read  at  the  rate  of  twenty-five  or  thirty  words 
per  minute,  the  best  practice  will  be  found  in  copying 
with  a  pen  and  ink  from  an  instrument  connected  with 
a  line  employed  in  transmitting  regular  commercial 
messages,  in  order  that  the  student  may  familiarize 
himself  with  the  usages  of  the  lines  and  the  minute 
details  of  actual  telegraphic  business. 

In  conclusion,  the  student  is  warned  against  falling 
into  the  common  error  of  expecting  great  results  from 
little  labor.  To  become  an  expert  operator  requires 
much  time  and  patience,  and  the  most  unwearied  appli- 
cation. Remember,  that  whatever  is  worth  doing  at  all 
is  worth  doing  well.  The  time  will  seldom  or  never  be 
found  when  a  thoroughly  competent  operator  cannot 
obtain  immediate  and  remunerative  employment,  how- 
ever overcrowded  the  lower  walks  _of  the  profession 
may  have  become. 


CHAPTER    IX. 


UECENT    IMPROVEMENTS    IN     TELEGRAPHIC     PRACTICE. 

160.  THE  AMERICAN  COMPOUND  .WIRE. — This  impor- 
tant improvement  in  telegraphic  conductors,  referred 
to  in  another  part  of  this  work  (135),  has,  within  two 
or  three  years  of  its  first  introduction,  become  so 
extensively  used  that  it  seems  likely  in  time  to  work  a 
complete  revolution  in  the  American  system  of  line 
construction.  This  wire  is  composed  of  a  core  of  steel 
enveloped  in  a  sheathing  of  pure  copper,  and  coated 
with  an  alloy,  of  which  tin  is  the  principal  ingredient, 
which  serves  to  protect  the  whole  from  oxidization. 
;  The  relative  strength  of  this  wire  is  more  than  50 
per  cent,  greater  than  that  of  iron  wire  of  equal  weight, 
and  its  conductivity  is  also  largely  in  excess  of  the 
latter.  If  we  take,  for  example,  a  No.  8  galvanized 
iron  wire,  the  gauge  now  usually  employed  in  this 
country  in  the  construction  of  the  best  lines,  and 
compare  it  with  a  compound  wire  of  nearly  similar 
electrical  capacity,  the  superiority  of  the  latter  will  be 
manifest. 


Weight 
per  mile. 

Tensile 
Strength. 

Conductivity. 

Poles 
per  mile. 

. 

Galvanized  Iron  Wire  (No.  8)  
American  Compound  Wire  (No.  8)  . 

375 

112 

1091 
514 

1 
1  07 

35 
23 

In  the  above  table  the  average  conductivity  of  a 
mile  of  No.  8  galvanized  wire  is  taken  as  1,  as  a  standard 
of  comparison.  The  last  column  shows  the  number  of 
poles  per  mile  which  will  give  the  same  percentage  of 
strain  upon  the  ultimate  strength  of  the  wire.  In 
practice,  however,  it  is  safe  to  reduce  the  proportionate 
number  of  poles  used  for  the  compound  wire,  as  the 


RECENT  IMPROVEMENTS  IN  TELEGRAPHIC  PRACTICE. 


105 


fiteel  core  is  much  more  homogeneous  and  less  liable 
to  fracture  on  account  of  flaws,  than  the  iron  wire. 

The  advantages  which  arise  from  increased  conduc- 
tivity of  the  line  wire  and  the  diminution  of  the  number 
of  points  of  insulation  and  support  are  fully  treated 
upon  in  another  part  of  this  work.  The  mechanical 
advantages  of  the  compound  wire  are  also  very  great. 
The  labor  of  handling  and  stringing  a  light  wire  is  much 
less  than  when  a  heavy  one  is  employed.  In  running 
the  wires  over  buildings,  a  mode  of  construction  which 
has  become  very  common  in  all  large  cities,  stretches 
may  safely  be  made  double  the  length  of  those  taken 
with  the  ordinary  wire,  and  yet  with  less  strain  upon 
the  insulators.  Another  important  point  in  favor  of 
this  wire  is  the  imperishable  nature  of  the  copper, 
which  is  the  exposed  metal.  It  is  well  known  that 
the  zinc  coating  of  galvanized  iron  wire  is  soon  de- 
stroyed near  the  sea-coast,  and  from  the  effects  of 
carbonic  acid  arising  from  the  combustion  of  coal  in 
cities  (137).  Copper,  under  the  same  conditions, 
remains  wholly  unimpaired.  Many  cases  occur  in  the 
construction  of  lines  in  which  transportation  is  an  item 
of  great  expense.  In  such  cases,  wire  of  the  same 
or  greater  conductivity  than  galvanized  iron,  weighs 
materially  less,  with  no  disadvantage  whatever  arising 
from  its  lightness. 

161.  The  following  table  exhibits  the  weight,  size, 
and  relative  strength  of  compound  wires,  equivalent  in 
conducting  power  to  the  ordinary  sizes  of  iron  wire 
used  in  telegraphic  construction. 


1 

6 

8 

f; 

6 

GALVANIZED  IRON  WIRE. 

COMPOUND  STEEL,  AND  COPPER  WIRE. 

Weight 
per  mile. 

Relative 
Strength. 

Weiirht 
per  mile. 

Relative 
Strength. 

Size  of 
Steel  Core. 

Size  of 
Compound. 

313 
375 
449 
525 

2.9 
2.9 
2.9 
2.9 

99 
112 
121 

147 

4.9 
4.6 
44 
4.5 

16 
16 
16 
15 

14 
14-1- 
13- 
12- 

106  RECENT    IMPROVEMENTS    IN   TELEGRAPHIC    PRACTICE. 

The  term  relative  strength,  used  in  the  preceding 
table,  is  the  quotient  obtained  by  dividing  the  strain 
which  would  break  the  wire  by  its  weight  per  mile. 

In  constructing  lines  with  the  compound  wire,  much 
care  should  be  used  in  making  the  joints  so  as  not  to 
separate  the  copper  sheathing  from  the  steel  core,  thus 
allowing  moisture  to  penetrate  to  the  steel  and  oxidize 
it.  This  may,  however,  be  guarded  against  by  care- 
fully soldering  the  joints. 

162.  THE  GRAVITY  BATTERY. — Several  modifications 
of  the  Daniell  battery  (19),  especially  adapted  to  tele- 
graphic use,  are  finding  much  favor  within  the  past  few 
years.  The  most  economical  and  generally  useful  of 
these  improved  forms  is  the  gravity  battery.  The  best 
arrangement  is  that  known  as  the  Callaud.  Another 
combination  very  closely  resembling  it,  and  giving 
nearly  as  favorable  results,  is  known  in  this  country  as 
the  Hill  battery.  In  these  elements  the  porous  cup  of 
the  Daniell  battery  is  entirely  dispensed  with,  the  two 


FIG.  56. 


solutions  being  prevented  from  mingling  by  the  differ- 
ence of  their  respective  specific  gravities.  The  zinc 
plate  of  the  Callaud  element,  in  the  form  of  a  short 
hollow  cylinder,  open  at  both  ends,  is  suspended  in  the 
upper  portion  of  the  containing  jar,  as  shown  in  Fig. 
56,  by  means  of  three  hooks  projecting  from  its  upper 
edge,  resting  upon  the  jar.  A  strip  of  copper  rolled 
into  a  spiral  form  is  soldered  to  a  copper  wire  covered 
with  gutta-percha,  forming  the  positive  pole  and  con- 
necting it  to  the  zinc  of  the  next  element. 


RECENT    IMPROVEMENTS    IN    TELEGRAPHIC    PRACTICE. 


107 


163.  The  manner  of  setting  up  this  battery  is  as 
follows : 

A  sufficient  quantity  of  soft  water  is  poured  into 
each  jar  to  fill  it  to  a  point  above  the  upper  surface 
of  the  zinc.  The  battery  should  now  be  placed  in  the 
position  which  it  is  to  permanently  occupy,  unless  this 
has  been  already  done.  After  the  connections  are 
made  and  everything  in  readiness,  about  three-quarters 
of  a  pound  of  sulphate  of  copper  in  lumps  of  the  size  of 
a  hickory  nut  or  larger,  is  dropped  in,  taking  care  that 
it  does  not  lodge  upon  the  zinc.  The  solution  of  sul- 
phate -of  copper  being  of  greater  specific  gravity,  will 
remain  at  the  bottom  of  the  jar.  The  battery,  after 
it  is  set  up,  should  be  kept  on  a  closed  circuit  for 
about  twelve  hours,  when  its  resistance  will  have  become 
reduced  so  that  the  force  will  be  available.  As  the  bat- 
tery continues  in  action,  the  sulphate  of  copper  solu- 
tion gradually  becomes  weaker  and  the  zinc  solution 
stronger.  It  is  therefore  necessary  from  time  to  time 
to  add  crystals  of  sulphate  of  copper,  and  to  remove  a 
portion  of  the  zinc  solution  and  replace  by  water.  A 
good  practical  rule  for  maintaining  this  battery  is  to 
always  see  that  the  stratum  of  liquid  around  and  in 
contact  with  the  copper  is  kept  of  a  blue  color.  The 
formation  of  transparent  crystals  upon  the  zinc  indi- 
cates that  the  point  of  saturation  of  the  zinc  solution 
has  been  reached  and  that  it  should  be  diluted  with 
water.  A  Baume  hydrometer  is  very  convenient  for 
determining  the  density  of  the  zinc  solution.  The  latter 
should  be  maintained  at  from  20°  to  30°  in  a  main 
battery,  and  from  15°  to  25°  in  a  local. 

It  often  occurs  in  using  this  battery  that  stalactites 
of  copper  attach  themselves  to  the  lower  edge  of  the 
zinc  and  hang  suspended  in  the  solution,  slowly  but 
constantly  increasing  in  length.  These  are  first  pro- 
duced by  a  deposit  of  copper  upon  the  zinc,  which  sets 
up  a  local  action  followed  by  a  rapid  decomposition  of 
the  solution  and  a  further  deposit  of  copper.  These 
should  be  removed  by  means  of  a  bent  wire  and  allowed 


108  RECENT    IMPROVEMENTS   IN    TELEGRAPHIC    PRACTICE.  . 

to  fall  to  the  bottom  of  the  jar,  as  they  occasion  a  use- 
less expenditure  of  sulphate. 

Absolute  quietude  is  essential  to  the  proper  per- 
formance of  this  battery.  A  slight  jar  will  cause  the 
solutions  to  mingle,  and  this  effect  will  be  followed  by 
a  rapid  deposition  of  metallic  copper  upon  the  zinc. 
When  the  zincs  are  removed  for  cleansing,  care  must  be 
taken  not  to  agitate  the  solution. 

Prof.  Hough,  of  the  Dudley  Observatory,  has  sug- 
gested the  use  of  sheet  lead  in  the  place  of  the  copper 
spiral,  as  it  is  cheaper  and  more  readily  cut  and  formed 
into  proper  shape.  There  is  no  perceptible  difference 
in  the  electro-motive  force  or  in  the  resistance  of  the 
battery  when  lead  plates  are  substituted  for  copper  in 
this  way. 

The  electro-motive  force  of  the  gravity  battery  is 
the  same  as  the  Daniell,  and  the  average  resistance 
when  in  good  working  condition  about  three  units. 

164.  SIEMENS'  UNIVERSAL  GALVANOMETER. — The  ap- 
paratus employed  for  the  measurement  of  electrical 
resistances  consists  essentially  of  a  standard  resistance, 
•which  is  used  for  the  purpose  of  comparison,  a  galva- 
nometer, by  which  the  result  is  indicated,  arid  a  galvanic 
battery.  In  the  different  methods  of  testing,  these 
appliances  are  arranged  in  various  ways,  as  particular 
circumstances  may  render  convenient  or  desirable. 
The  various  methods  of  testing  in  use  may  be  classified, 
however,  under  three  heads,  viz. : 

1.  By  the  angles  of  deflection  of  a  galvanometer 
needle. 

2.  By  the  differential  galvanometer. 

3.  By  the  Wheatstone  bridge,  or  electrical  balance. 
The  first-named  method  is  the  simplest  in  principle, 

and,  with  proper  care,  gives  very  accurate  results.  It 
is  not  so  convenient  as  the  other  two  methods  for  ordi- 
nary use,  but  is  applicable  more  especially  for  the 
measurement  of  very  high  resistances,  such  as  insula- 
tors, etc.  It  is  also  employed  in  measuring  the  inter- 
nal resistance  of  batteries.  As  the  strength  of  the 


RECENT   IMPROVEMENTS   IN   TELEGRAPHIC   PRACTICK.  109 

current  passing  through  the  coils  of  a  galvanometer  is 
always  proportionate  to  the  sine  or  tangent  of.the  angle 
of  deflection  of  the  needle,  and  is  also  inversely  pro- 
portional to  the  resistance  in  circuit,  it  follows  that  if 
we  find  the  deflection  with  a  certain  known  resistance 
in  circuit  to  be  only  22°,  and  we  then  substitute  for 
this  known  resistance  an  unknown  one,  which  gives  us 
a  deflection  of  39°.  the  tangent  of  the  latter  will  be 
twice  that  of  the  former,  and  the  unknown  resistance 
is  consequently  found  to  be  half  that  of  the  known  re- 
sistance. (170.) 

The  second  method  is  very  convenient  and  is  much 
used,  although  not  equal  in  strict  accuracy  to  the  third 
method.  The  galvanometer  coils  are  wound  with  two 
wires  of  the  same  length  and  resistance,  insulated  from 
each  other  with  the  utmost  care.  The  needle  is  there- 
fore surrounded  by  an  equal  number  of  convolutions  of 
each  wire,  which  are  also  equidistant  from  it.  One 
end  of  each  wire  is  connected  to  the  battery,  but  in 
such  a  manner  that  the  current  flows  in  opposite  direc- 
tions through  the  two  wires.  When,  therefore,  the  two 
currents  are  of  equal  strength,  one  tends  to  deflect  the 
needle  to  the  right  and  the  other  to  the  left  with  equal 
power,  and  the  needle  remains  at  rest.  If  we  insert 
an  unknown  resistance  into  the  circuit  of  one  of  these 
wires  the  current  is  weakened,  as  is  also  its  effect  on 
the  needle,  which  no  longer  remains  balanced  and  at 
rest,  but  is  deflected  to  one  side.  If  we  now  insert  a 
series  of  known  resistances  into  the  circuit  of  the  other 
wire,  until  the  needle  is  again  brought  into  equilibrium, 
we  are  certain  that  the  unknown  resistance  in  one  cir- 
cuit is  exactly  equal  to  the  known  resistance  in  the 
other.  (122.) 

The  third  method  is  susceptible  of  the  greatest  accu- 
racy of  measurement,  when  proper  precautions  are  ob- 
served. The  connections  of  the  "bridge"  are  arranged 
as  follows : 

We  will  suppose  the  wires  A  B  C  D  (Fig.  57),  arranged 
in  the  form  of  a  parallelogram,  to  be  of  exactly  equal 


110 


RECENT  IMPROVEMENTS  IN  TELEGRAPHIC  PRACTICE. 


resistance.  If  we  attach  the  two  poles  of  a  battery,  E, 
to  the  points  1  and  2,  its  current  will  divide  at  1,  half 
of  it  going  through  A  B,  and  the  other  half  going 
through  C  D,  to  the  point  2,  and  thence  to  the  other 
pole  of  the  battery.  The  galvanometer  Gr,  placed  on  a 
wire  connected  across  from  3  to  4,  will  not  be  affected 
as  long  as  A  B  is  equal  to  C  D,  no  matter  what  the 
absolute  resistance  may  be. 

Again,  when  A  bears  the  same  proportion  to  C  that 
B  does  to  1),  or  when  A:  C: :  B:  D,  no  current  will 
pass  from  3  to  4  through  the  galvanometer.  If  the 
resistance  of  A  be  made  10,  that  of  B  1,  of  C  1,000, 


FIG.  57. 

and  of  D  100,  the  total  resistance  of  A  B  will  now  be 
11.  and  that  of  C  1,100  ;  but  the  tension  in  each 
branch  will  have  fallen  in  the  same  proportion  at  the 
points  3  and  4,  and  no  current  will  pass  between  those 
points. 

If,  therefore,  we  insert  a  known  standard  resistance 
in  the  wire  B,  and  an  unknown  one  in  D,  and  divide  a 
given  resistance  between  A  and  C  until  we  get  no  effect 
upon  the  galvanometer  needle,  we  are  then  certain  that 
the  resistance  of  A  bears  the  same  proportion  to  that 
of  B  as  the  known  resistance  does  to  the  unknown  one 
D,  which  may  be  readily  calculated  by  proportion  or 
the  "rule  of  three." 

It  is  not  necessary,  of  course,  that  the  wires  should 
be  arranged  in  the  exact  form  shown,  nor  in  fact  is  it 


RECENT    IMPROVEMENTS    IN   TELEGRAPHIC    PRACTICE.  Ill 

often  done,  but  the  principle  is  more  easily  explained 
and  remembered  when  thus  arranged. 

165.  The  Universal  Galvanometer  of  Dr.  Werner 
Siemens  is  constructed  upon  the  principle  of  the  Wheat- 
stone  bridge,  just  described,  but  its  connections  are  so 
arranged  that  it  may  be  used  when  desired  for  the 
method  of  deflections  first  mentioned. 

The  galvanometer  is  mounted  upon  a  disk  of  slate 
about  six  inches  in  diameter.  A  groove  in  the  edge  of 
this  disk,  extending  about  half  way  round  the  circum- 
ference, contains  a  wire  of  considerable  resistance, 
which  corresponds  to  the  wires  A  and  C  in  the  above 
diagram.  A  small  platina  roller,  mounted  upon  a 
radial  arm,  is  connected  to  one  pole  of  the  battery,  and 
forms  the  connection  with  the  wire  A  C,  as  shown  at  1 
in  the  diagram.  The  wire  corresponding  to  B  is  sup- 
plied with  three  standard  resistances  of  10,  100,  and 
1,000  Siemens'  units,  respectively,  either  of  which  may 
be  placed  in  circuit  at  pleasure,  by  means  of  contact 
plugs.  The  wire  D  is  provided  with  binding  screws  for 
the  attachment  of  the  wire,  or  other  resistance  which 
it  is  required  to  measure.  The  galvanometer  consists 
of  a  pair  of  very  delicate  astatic  needles,  suspended  by 
a  fine  silk  fibre.  The  coil  has  a  resistance  of  1 00  Sie- 
mens' units. 

The  radial  arm  carrying  the  platina  roller  also  car- 
ries a  pointer  or  index,  moving  over  a  scale  upon  the 
circumference -of  the  slate  disk,  which  is  divided  into 
300  degrees,  and  which  may  be  read  to  one-fifth  of  a 
degree  by  means  of  a  vernier. 

In  using  the  instrument,  the  standard  resistance  cor- 
responding most  nearly  to  the  unknown  resistance 
which  is  to  be  measured  is  unplugged  and  placed  in 
circuit  at  B  (Fig  57),  while  the  unknown  resistance 
itself  is  inserted  at  D.  The  radial  arm  carrying  the 
platina  roller  1  is  now  moved  towards  A  or  C,  until 
the  needle  is  balanced.  The  proportion  of  A  to  C  is 
then  read  off  the  scale,  from  which  the  proportion  of  B 


112  RECENT    IMPROVEMENTS    IN   TELEGRAPHIC    PRACTICE. 

to  D  is  readily  calculated,  or  is  taken  from   a  printed 
table  furnished  with  the  instrument. 

This  galvanometer  may  also  be  employed  for  com- 
paring electro-motive  forces,  according  to  the  method 
of  Poggendorff,*  and  is  applicable  to  almost  any  pur- 
pose for  which  an  apparatus  of  the  kind  may  be  re- 
quired. 

This  instrument  usually  has  a  constant  of  about  four 
degrees,  with  one  Danieli's  cell  through  1,000,000  Sie- 
mens' units.  When  used  as  a  Wheatstone  bridge,  its 
range  of  measurement  is  from  O.L7  to  59,000  Siemens' 
units.  Higher  resistances,  such  as  insulators,  may  be 
measured  by  the  method  of  deflections.  The  entire 
apparatus  (except  the  battery)  occupies  a  space  only 
nine  inches  in  diameter,  and  the  same  in  height.  It  is 
packed  in  a  neat  case,  and  can  be  carried  about  with 
great  convenience. 

166.  POPE  &  EDISON'S  PRINTING  TELEGRAPH. — Type- 
printing  telegraph  instruments,  which  were  formerly 
employed  for  commercial  telegraphing,  have,  within 
two  or  three  years,  been  extensively  introduced,  in  a 
modified  and  simple  form,  in  the  various  branches  of 
private  telegraphy,  with  great  success.  One  of  the 
best  of  these  is  that  of  Pope  <fe  Edison,  which  is  shown 
in  Fig.  58. 

The  different  portions  of  the  apparatus,  with  the 
exception  of  the  battery,  are  mounted  upon  a  small 
table,  similar  in  size  and  construction  to  that  of  an 
ordinary  sewing-machine.  At  the  back  of  the  table 
are  six  binding  screws  to  which  are  attached  the  line 
and  ground  wires,  and  the  wires  leading  to  the  main 
and  local  batteries.  The  instrument  operates  upon 
what  is  known  as  the  "  open  circuit  principle,"  each 
station  transmitting  with  its  own  main  battery — the 
line  at  the  receiving  station  being  connected  directly 
through  the  relay  to  the  ground  without  the  interven- 
tion of  a  second  battery. 

*  See  Clark's  '-Electrical  Measurement,"  p.  105.  Also  Sabine's  "Elect 
Tel.,'1  p.  320. 


I 

a: 

« ; 

H 


RECENT   IMPROVEMENTS    IN   TELEGRAPHIC    PRACTICE.  113 

The  printing  apparatus  is  placed  upon  a  circular 
iron  base  in  the  centre  of  the  table.  In  front  of  it  is 
placed  a  dial  containing  the  letters  of  the  alphabet, 
arranged  in  a  circle  and  provided  with  an  index  or 
pointer,  mounted  upon  a  horizontal  shaft.  This  shaft 
also  carries  a  type  wheel,  with  the  letters  of  the  alpha- 
bet engraved  upon  its  periphery,  and  a  scape-wheel, 
with  rachet-shaped  teeth,  corresponding  in  number  to 
the  characters  upon  the  type  wheel  and  dial.  An 
electro-magnet  beneath  the  base  is  provided  with  an 
armature,  attached  to  a  vibrating  lever,  the  latter 
armed  with  pawls  or  clicks,  so  arranged  in  relation  to 
the  scape-wheel  that  every  time  the  electro-magnet 
attracts  its  armature,  the  wheel  is  made  to  revolve  a 
distance  of  one  tooth,  and  the  type  wheel  and  index 
upon  the  same  shaft  a  distance  of  one  letter.  At  the 
extreme  right  of  the  circular  base,  and  partly  beneath 
it,  as  seen  in  the  engraving,  is  placed  a  second  electro- 
magnet, whose  armature  lever  passes  in  a  horizontal 
direction  below  the  type  wheel.  Directly  underneath 
the  type  wheel  an  india-rubber  pad  is  fixed  upon  the 
lever,  by  means  of  which  an  impression  of  the  letter 
which  is  opposite  it  upon  the  type  wheel  may  be  taken 
in  the  manner  hereafter  to  be  described.  This  lever  is 
also  provided  with  a  simple  mechanical  device  for 
moving  the  paper  forward  the  proper  distance,  as  the 
impression  of  each  successive  character  is  imprinted 
upon  it.  This  may  be  seen  at  the  left  of  the  printing 
apparatus.  The  type  wheel  is  provided  with  a  suitable 
inking  roller,  as  shown  in  the  engraving. 

It  will  thus  be  understood  that  the  printing  mechan- 
ism is  operated  by  two  distinct  electro-magnets,  one 
of  which  is  so  arranged  that  its  successive  pulsations 
may  be  made  to  advance  the  index  step  by  step  to 
any  required  letter,  while  the  other  forces  the  strip 
of  paper  against  the  inked  type  upon  the  wheel,  after 
it  has  been  moved  to  the  proper  position  by  the  first 
magnet.  The  type  wheel  is,  of  course,  so  arranged  in 
reference  to  the  index  upon  the  same  shaft,  that  when 


114  RECENT   IMPROVEMENTS    IX   TELEGRAPHIC    PRACTICE. 

the  latter  points  to  any  given  letter  the  correspond- 
ing letter  upon  the  type  wheel  is  opposite  the  impres- 
sion pad. 

These  two  electro-magnets  are  placed  in  the  circuit 
of  a  local  battery,  which  is  brought  into  action  by  a 
relay  placed  in  the  main  line  circuit,  as  in  the  ordinary 
Morse  apparatus.  The  relay  is  shown  at  the  right  of 
the  printing  mechanism,  covered  by  a  small  glass 
shade.  It  is  the  same  in  principle  as  the  ordinary 
Morse  relay,  with  the  addition  of  a  device  termed 
the  "polarized  switch,"  which  consists  of  a  perma- 
nently magnetized  steel  bar,  pivoted  between  the  poles 
of  the  relay  magnet,  and  forming  a  part  of  the  local 
circuit.  This  is  attracted  to  the  right  or  left  accord- 
ing to  the  polarity  of  the  relay  magnet,  which  itself, 
in  turn,  depends  upon  the  direction  of  the  electrical 
current  in  the  main  circuit.  The  polarized  switch 
determines  the  direction  of  the  local  circuit,  causing  it 
to  pass  through  the  magnet  for  moving  the  type 
wheel,  or  through  the  impression  magnet,  as  may  be 
required. 

Two  lever  finger  keys,  with  vulcanite  knobs,  are 
placed  on  each  side  of  the  printing  apparatus,  as 
shown  in  the  engraving  ;  and  it  is  by  means  of  these 
that  the  instrument  is  operated.  They  are  connected 
to  opposite  poles  of  the  main  battery  in  such  a  man- 
ner that,  by  depressing  the  right  hand  key,  the  posi- 
tive pole  of  the  battery  is  connected,  through  the  relay 
magnet  to  the  line,  and  the  negative  to  the  ground, 
while  the  left  hand  key,  on  the  contrary,  sends  a  neg- 
ative current  through  the  relay  and  line  in  the  same 
manner. 

The  mode  of  operating  the  instrument  is  exceed- 
ingly simple.  By  depressing  the  right  hand  key  a 
sufficient  number  of  times  in  rapid  succession,  a  series 
of  positive  currents  is  sent  through  the  relays  at  both 
ends  cf  the  line,  which  are  repeated  upon  the  local 
circuits  of  both  instruments.  The  positive  currents 
deflect  the  polarized  switches  to  the  left,  so  that  the 


RECENT   IMPROVEMENTS    IN   TELEGRAPHIC    PRACTICE.  115 

local  circuit  is  directed  into  the  type-wheel  magnet. 
The  index  and  type  wheel  of  both  instruments,  there- 
fore, advance  one  letter  every  time  the  key  is  de- 
pressed, and  they  may  thus  be  readily  brought  to  any 
desired  letter.  When  this  has  been  done,  the  left  hand 
key  is  depressed,  which  sends  a  negative  current, 
reversing  the  polarized  switch,  and  the  local  circuit 
is  directed  through  the  printing  magnet,  producing 
the  impression  of  that  letter  upon  the  strip  of  paper, 
and  this  process  may  be  continued  indefinitely. 

Suitable  arrangements  are  provided  for  bringing  the 
type  wheels  of  the  two  instruments  together  in  case 
they  should  accidentally  be  thrown  out  of  correspond- 
ence. 

These  instruments  are  entirely  automatic  in  their 
action,  and  a  despatch  may  be  printed  at  the  remote 
end  of  the  line,  in  the  absence  of  an  attendant.  In  the 
event  of  any  derangement  of  the  printing  apparatus,  it 
may  be  used  as  a  dial  instrument  as  conveniently  as  if 
especially  constructed  for  that  purpose. 

The  battery  is  always  disconnected,  except  at  the 
moment  of  working,  and  therefore  is  consumed  but 
slowly.  Other  systems  require  the  battery  to  be  con- 
stantly connected  to  the  line  whether  working  or  idle. 
A  battery  of  two  carbon  cells  per  mile,  and  in  many 
cases  even  less,  will  work  the  instrument  and  remain 
in  action  front  one  to  four  weeks  without  renewal, 
according  to  the  amount  of  telegraphing  done  upon 
the  line. 

It  is  impossible  for  the  main  circuit  to  be  acciden- 
tally left  open.  Only  one  adjustment — that  of  the 
tension  spring  of  the  relay — is  required  after  the 
instrument  is  first  put  in  operation,  and  that  but  rarely 
on  lines  of  ordinary  length. 


CHAPTER!. 


APPENDIX    AND     NOTES. 


167.  THE  EQUIPMENT  OF  TELEGRAPH  LINES. — The 
satisfactory  performance  of  any  given  telegraphic  cir- 
cuit depends  largely  upon  the  maintenance  of  a  proper 
relation  between  the  respective  resistances  of  the  line, 
instruments,  and  batteries.  There  is  in  all  cases  an  as- 
certainable  definite  proportion  between  these,  which 
gives,  theoretically,  the  best  result  with  the  least  ex- 
penditure ;  to  which  practice  should  always  be  made  to 
approximate  as  nearly  as  possible.  The  disregard  of 
the  well-established  laws  of  electrical  and  magnetic 
action  is  not  only  the  source  of  grave  difficulties  in  the 
practical  operation  of  lines,  but  also  entails  an  enor- 
mous waste  of  material  and  supplies. 

It  is  one  of  the  fundamental  laws  of  the  electric  cir- 
cuit, that  with  a  given  resistance  of  conducting  wire  and 
battery,  the  maximum  magnetic  force  is  developed  when 
the. total  resistance  of  the  coils  of  the  electro- magnet  or 
magnets  is  equal  to  the  resistance  of  the  other  portions  of 
the  circuit,  i.  e.,  the  batteries  and  conducting  wires.  (173.) 

The  resistance  of  the  conductor,  which  must  of  ne- 
cessity, always  form  a  large  proportion  of  the  total 
resistance  in  every  main  circuit,  is  in  practice  deter- 
mined within  certain  well-defined  limits,  by  considera- 
tions of  distance,  mechanical  construction,  and  first 
cost.  It  therefore  becomes  necessary  to  adjust  the 
resistance  of  the  remaining  parts  of  the  circuit  with 
reference  to  that  of  the  conductor,  which  in  practice 
usually  ranges  from  10  to  20  units  per  mile.  With  the 


APPENDIX    AXD    NOTES. 


117 


No.  9  galvanized  iron  wire  generally  used,  it  approxi- 
mates closely  to  the  latter  figure. 

The  resistance  of  the  batteries  forms  but  a  very  small 
portion  of  the  total  resistance  in  an  ordinary  main  cir- 
cuit, and  admits  of  comparatively  little  variation,  so 
that  the  actual  problem  which  presents  itself,  is  to  deter- 
mine the  proper  resistance  of  the  relays  when  the 
resistance  of  the  conductor  is  given,  and  the  form  of 
battery  which  will  supply  the  necessary  electrical  power 
for  operating  the  line  with  the  least  expenditure  of 
materials  and  labor. 

The  size  of  the  conductor  having  been  fixed  upon, 
this  taken  in  connection  with  the  length  will  determine 
its  total  resistance.  The  combined  resistance  of  the 
relays  should  be  made  to  equal  this  amount  as  nearly 
as  possible.  It  is  hardly  necessary  to  add  that  the  re- 
sistance of  the  different  relays  should  be  uniform  in 
respect  to  each  other.  With  good  rekys  the  amount 
of  battery  required  to  operate  the  main  circuit  should 
not  exceed  1  cell  of  Grove  or  Carbon  battery  for  each 
150  units  resistance,  and  will  generally  be  less  than 
this.  About  double  this  number  of  the  Daniell,  Hill, 
or  Callaud  battery  will  be  needed. 

For  example,  suppose  it  is  required  to  construct  a 
telegraph  line  300  miles  in  length,  with  15  stations. 
If  No.  9  iron  wire  is  used  as  a  conductor  its  resistance 
will  be  say  300  X  20  =  6000  units.  The  resistance  of 
all  the  relays  being  made  equal  to  that  of  the  line,  we 
have  as  the  proper  resistance  for  each  relay  -6yf  °  =  400 
units.  The  amount  of  battery  required  will  be  -f£{j-°- 
=80  cups  of  Grove  or  Carbon,  or  about  160  cups  of 
Daniell,  Hill,  or  Callaud. 

The  approximate  average  resistance,  and  compara- 
tive electro-motive  force  of  the  different  batteries  in 
use  is  as  follows,  the  Grove  battery  being  taken  as  the 
standard  at  100  : 

Electromotive 
Resistance.  force. 

Grove 5  units.  100 

Bi-Chromate  or  Carbon 10       "  107 

Danii-11 2.0       "  56 

Callaud    ..  3.0      "  56 


118 


APPENDIX   AND    NOTES. 


These  figures  refer  to  the  ordinary  sizes  of  the  Grove 
and  Carbon  battery,  and  to  the  Daniell  and  Callaud 
when  adapted  to  a  jar  eight  inches  high  and  six 
inches  inside  diameter.  Although  the  resistance  of  the 
battery  when  included  in  a  single  main  circuit  of  the 
usual  length,  has  but  little  influence  upon  the  effec- 
tive strength  of  the  current  as  a  whole,  yet  in 
local  circuits,  and  in  main  batteries  from  which  a 
number  of  lines  are  worked  at  the  same  time  (110), 
it  becomes  an  essentially  important  element  in  the 
calculation. 

Another  important  law  of  electrical  action,  which 
applies  especially  to  instruments  which  are  to  be  worked 
by  a  local  circuit,  is  the  following  : 

The  greatest  effective  force  of  any  given  battery  is 
developed  when  the  sum  of  all  the  external  resistances 
in  the  circuit  is  equal  to  the  internal  resistance  of  the 
battery. 

In  a  local  circuit  there  are  practically  no  resistances 
except  those  of  the  battery  and  magnet,  and  it  is  there- 
fore obvious  that  these  should  be  so  adjusted  as  to  equal 
each  other  as  nearly  as  possible.  Tested  by  this  rule,  a 
great  portion  of  the  sounders,  registers,  and  repeaters, 
in  use  in  this  country,  will  be  found  to  have  magnets 
of  too  low  resistance,  most  of  them  being  adapted  to 
the  use  of  a  local  of  1  Grove  cell,  although  nearly  all 
the  local  batteries  in  use  are  composed  of  2  or  "6  cells 
of  Daniell.  Such  a  magnet  will  only  partially  develop 
the  effective  force  of  a  Daniell  battery,  and  still  less 
that  of  a  Callaud  or  Hill. 

The  sizes  of  copper  wire  generally  used  in  local 
helices  vary  from  No.  19  to  22,  American  gauge,  and 
the  resistance  from  0.5  units  to  4  units.  The  most 
usual  resistance  is  about  1  unit.  If  we  take  a  sounder 
of  this  resistance  and  apply  a  cell  of  Grove  battery,  we 
have  the  following  result : 

Bcsistance  of  magnet 1  unit. 

"  "     battery 1     " 

Total...  ..  2     " 


APPENDIX   AND   NOTES.  119 

Calling  the  electro-motive  force  100,  and  dividing 
this  by  the  resistance,  we  get  50  as  the  effective  strength. 
If  we  take  the  same  sounder  and  apply  a  Daniell  ele- 
ment with  2  units  resistance  the  total  resistance  will  be 
3,  the  electro-motive  force  56,  and  the  quotient  or  effec- 
tive force  18.6,  but  little  more  than  one-third  that  of 
the  Grove.  With  2  Daniell  cells  we  have — 

Resistance  of  magnet 1  unit. 

"  "  battery t 4     " 

Total ~5     " 

The  electro-motive  force  of  2  cells  will  be  56  x  2  = 
112,  and  dividing  this  by  the  resistance,  5,  we  have 
22.4.  With  2  Callaud  cells  the  effect  would  be  still 
less,  in  fact  only  16. 

Now  let  us  take  the  same  sounder,  and  remove  the 
helices  of  No.  19  wire,  which  give  a  resistance  of  1 
unit,  and  rewind  them  with  No.  23  wire,  and  observe 
the  effect.  With  a  given  strength  of  current,  the  mag- 
netic effect  is  proportional  to  the  number  of  convolu- 
tions, and  the  latter  increase  inversely  as  the  square  of 
the  diameter  of  the  wire.  The  resistance  of  the  wire 
also  increases  as  its  length,  and  inversely  as  the  square 
of  its  diameter.  The  squares  of  the  respective  diame- 
ters would  be  as  follows  : 

No.  19 00128381 

"    23 00051076 

The  average  length  of  each  convolution  in  a  helix 
of  a  given  size  will  be  the  same  with  any  sized  wire. 
The  length  being  in  inverse  proportion  to  the  square 
of  the  diameter,  the  resistance  due  to  the  increased 
length  will  be 

.00051076  :  .00128881  :  :  1  unit  :  2.52  units. 

But  the  resistance  is  further  increased  in  inverse  pro- 
portion to  the  square  of  the  diameter  of  the  wire,  there- 
fore 

.00051076  ;   .00128881  :  :  2.52  :   6.3 


120  APPENDIX   AND    NOTES. 

6.3  units  would,  therefore,  be  the  resistance  of  the 
new  helices.  This  is  not  strictly  accurate,  as  no 
allowance  has  been  made  for  the  spaces  between  the 
convolutions,  which  occupy  more  room  in  the  coil 
when  finer  wire  is  used,  and  somewhat  reduce  the 
number  of  convolutions  as  well  as  the  length  and  resist- 
ance of  the  wire.  We  will,  therefore,  call  the  resist- 
ance of  the  new  helices  6  units.  This  resistance  will 
give  the  greatest  possible  effect  obtainable  with  2  Gal- 
laud  cells,  which  will  be  as  follows : 

Resistance  of  magnet 6  units. 

"  battery.      6     " 

Total  resistance...     12     " 

Divide  the  electro-motive  force  112 

=  9.3 

By  the  total  resistance 12 

But  the  magnetic  effect  is  increased  by  the  greater 
number  of  convolutions  in  the  proportion  of  the 
squares  of  the  diameters,  or  as  2.52  to  1.  Therefore 
9.3  x  2.52  =  23.43.  This  is  greater  than  the  magnetic 
effect  of  2  Daniell  cells  upon  the  sounder  of  1  unit 
resistance,  which  we  before  found  to  be  22.4.  Making 
some  deduction  for  the  slight  decrease  in  the  number 
of  convolutions,  owing  to  the  greater  number  of  spaces, 
we  may  consider  the  actual  magnetic  effect  to  be  the 
same  in  both  cases.  Experience  has  shown  that  this  is 
amply  sufficient  to  operate  a  well-constructed  sounder 
or  register. 

In  the  above  calculations  the  resistance  of  the  Daniell 
is  given  as  2  units.  It  is  actually  over  3,  except  when 
the  porous  cell  is  defective,  or  so  excessively  porous  as 
not  to  separate  the  liquids  properly.  The  Callaud  is 
also  given  as  3  units,  but  in  point  of  fact  does  not  ex- 
ceed 2  after  it  has  been  2  weeks  in  use.  The  resist- 
ance of  the  different  Callaud  cells  is  very  uniform, 
while  cells  of  the  ordinary  form  of  Daniell  will  often 
vary  widely  under  precisely  similar  conditions.  Some- 
times one  cell  will  measure  10  units,  and  another 


APPENDIX   AND   NOTES.  121 

only  2,  owing  principally  to  difference  in  the  quality 
of  the  porous  cups.  A  cell  of  high  resistance  will 
diminish  instead  of  increasing  the  effect  in  a  local 
circuit. 

The  obvious  advantage  of  using  the  Callaud  battery 
for  local  circuits  in  connection  with  a  magnet  whose 
resistance  is  properly  adjusted  to  it,  consists  in  its  great 
economy,  the  expense  of  maintenance  not  being  more 
than  one-fifth  as  great  as  when  the  ordinary  Daniell 
is  employed.  The  above  calculations  show  that  a 
great  saving  can  be  made  when  the  Daniell  itself  is 
used,  by  regulating  the  resistance  of  the  magnets  to  cor- 
respond with  that  of  the  battery. 

1 68.  THE  WORKING  CAPACITY  OF  TELEGRAPH  LINES. — 
In  order  to  secure  the  best  possible  result  in  the  work- 
ing of  telegraph  lines  we  must  keep  down  the  resist- 
ance of  the  conductors  in  the  circuit  (42),  and  increase 
the  resistance  of  the  insulation  (90)  to  the  greatest 
practicable  extent.  In  other  words,  the  resistance  must 
be  as  small  as  possible  in  the  route  we  wish  the  electric 
current  to  travel,  and  as  great  as  possible  in  every 
other  direction.  The  practical  working  value  of  a  tele- 
graph line  is  the  margin  between  the  joint  resistance  of  the 
conductor  and  the  insulation,  and  that  of  the  insulation 
alone.  The  tension  of  the  retracting  spring  of  the 
relay  armature,  when  upon  a  "working  adjustment," 
is  the  measure  of  this  margin  or  difference.  It  is  evi- 
dent that  this  margin  may  be  increased  in  two  ways, 
viz.  : 

1.  By  increasing  the  insulation  resistance. 

2.  By  decreasing  the  resistance  of  the  conductor. 

For  example,  suppose  a  line  of  telegraph  100  miles 
in  length — the  weather  being  rainy.  Suppose  that  the 
conductor  has  a  resistance  of  20  units  per  »mile,  while 
the  resistance  of  the  insulators  is  1,000,000  units  per 
mile.  Let  the  receiving  magnet  and  battery  be  situ- 
ated at  one  extremity  of  the  line  and  the  key  at  the 
other.  When  the  key  is  closed,  the  force  acting  upon 


122  APPENDIX   AND    NOTES. 

the  armature  of  the  magnet  is  in  proportion  to  the 
quantity  of  electricity  leaving  the  battery  and  passing 
through  the  magnet  to  the  line,  and  this  quantity  is 
made  up  of  that  escaping  through  the  insulation  along 
the  line,  in  addition  to  that  going  through  the  con- 
ductor to  the  other  end  of  the  route.  When  the  key  is 
open,  the  force  exerted  upon  the  armature  is  due  to  the 
current  passing  through  the  insulation  alone.  The 
effective  working  strength  is  therefore  the  difference 
between  the  attractive  forces  acting  upon  the  armature, 
when  the  key  is  opened,  and  when  it  is  closed  at  the 
other  end  of  the  line — or,  in  other  words,  the  working 
margin  is  the  difference  between  the  sum  of  the  forces  dv# 
to  the  joint  conductivity  of  the  wire  and  insulators  and  that 
of  the  insulators  alone  (104). 

Thus,  in  the  case  cited : 

The  total  resistance  of  the  wire  is 2,000  units. 

"  insulation 10,000      " 

The  joint  resistance  of  wire  and  insulators  is 1,666      " 

The  strength  of  current  being  inversely  proportional 
to  the  resistance,  it  will  be  as  follows : 

When  key  at  other  end  is  closed 100.00 

"  "    open 16.66 


Difference,  or  effective  working  margin. 


It  is  not  the  absolute  resistance  of  the  conductor  or 
of  the  insulators  that  determines  the  value  of  a  line. 
It  is  operated  by  the  marc/in  or  difference  between  these 
two  values  (101).  It  is  important  that  this  should  not 
be  lost  sight  of. 

Now  let  us  observe  the  effect  of  substituting  a  wire 
of  twice  the  weight,  having  a  resistance  of  only  10 
units  per  mile.  We  now  have  : 

Total  resistance  of  wire  1,000  units. 

''  "    insulation  (as  before')..'...'..."..   10,000     " 

Joint  resistance...  909     " 


APPENDIX   AND    NOTES. 


123 


The  proportionate  strength  of  current  will  become 

When  key  is  closed 100.00 

"          ""      open 9.09 


Difference 


We  have  given  the  strength  of  current  with  key 
closed  as  100  iu  both  the  above  cases,  in  order  to  show 
the  proportionate  increase  of  margin.  The  absolute 
strength  of  current  in  the  two  cases  is  as  100  to  183, 
an  increase  of  83  per  cent.,  while  the  increase  of  work- 
ing margin  is  only  9  per  cent. 

We  will  now  take  the  result  of  an  actual  measure- 
ment. A  new  No.  9  galvanized  wire,  1L5  miles  in 
length,  on  a  clear  and  fine  day,  gave  a  resistance  of 
2,400  units,  or  about  21  units  per  mile.  On  the  same 
poles  was  a  No.  10  plain  wire,  which  had  been  in  use 
nineteen  years.  This  wire,  including  eight  instruments 
in  circuit,  gave  a  resistance  of  13,300  units.  In  a  rain 
the  insulation  resistance  of  the  good  wire  measured 
15,300  units,  and  the  bad  wire  19,650. 

The  joint  resistance  of  the  good  wire  and  its  insula- 
tors was  2,077.  The  proportion  of  current  escaping 
by  the  insulators  was  to  the  whole  current  as  13.51  to 
100,  giving  a  margin  to  work  on  of  86.49. 

The  joint  resistance  of  the  bad  wire  and  its  insula- 
tors was  7,982.  The  proportion  of  escape  to  the 
whole  current  was  as  40  to  100,  giving  but  60  percent, 
as  an  available  working  margin.  This  wire  could  not 
be  worked  except  when  the  other  circuits  on  the  same 
poles  remained  idle,  either  closed  or  open.  The  good 
wire  was  worked  without  difficulty.  The  escape  was 
apparent,  but  was  not  sufficiently  great  to  cause  any 
serious  inconvenience.  The  relative  working  margins 
were  in  the  proportion  of  86.49  to  60. 

On  a  clear  and  cold  day  the  insulation  of  the  good 
wire  showed  a  resistance  of  2,400,000  units,  the  work- 
ing margin  being  99.99.  The  bad  wire  showed  an 
insulation  resistance  of  1,700,000  units,  the  working 
margin  being  99.93.  The  difference  in  this  case 


124  APPEXDIX    AXD    NOTES. 

between  the  two  wires  was  only  00.06,  an  amount  not 
appreciable  in  practice.  The  poor  wire  worked  as  well 
as  the  good  one,  but  the  current  was  not  so  strong. 
This  difference  could  be  compensated  for  by  increasing 
the  battery  on  the  former. 

In  the  above  instance  we  have  two  wires  on  the 
same  poles.  One  is  new  and  a  good  conductor,  the 
other  old  and  a  poor  conductor.  In  fine  weather  the 
insulation  of  the  new  wire  is  the  most  perfect,  but  the 
difference  in  their  working  is  inappreciable.  In  rain, 
although  the  insulation  of  the  old  wire  is  actually 
the  best,  yet  it  does  not  work  nearly  so  well  as 
the  new  wire,  and  this  is  attributable  solely  to  the 
fact  that  the  new  wire  has  a  much  greater  conductive 
capacity. 

Take  another  example,  also  from  actual  measure- 
ment :  A  new  wire,  150  miles  in  length,  on  a  clear 
day  gave  a  resistance  of  2,200  units.  On  the  same 
poles  was  an  old  rusty  No.  11  wire,  which  gave  a  re- 
sistance of  23,500  units.  On  a  very  wet  day  the  insu- 
lation resistance  of  the  new  wire  was  4,800  units,  and 
of  the  old  wire  32,000  units.  The  working  margin  of 
the  new  wire  was  78,  and  that  of  the  old  wire  60.  In 
this  case  the  amount  of  current  escaping  over  the 
insulators  of  the  new  wire  was  2.7  times  that  passing 
through  the  old  wire  and  its  insulators  combined  !  In 
other  words,  the  current  with  key  open  on  the  new 
wire  was  nearly  three  times  as  strong  as  on  the  old 
wire  when  the  key  was  closed. 

In  these  examples  the  resistance  of  the  batteries  and 
instruments  has  not  been  taken  into  account,  as  they  do 
not  materially  affect  the  results. 

169.  THE  ELECTRICAL  TENSION  OF  TELEGRAPHIC  BAT- 
TERIES AND  LINES. — In  another  part  of  this  work  (8)  it 
was  briefly  stated  that  the  electrical  tension  of  a  battery, 
or  its  power  of  overcoming  resistance,  is  increased  in 
direct  proportion  to  the  number  of  elements  of  which 
the  battery  consists.  Suppose  we  have  a  battery  of 
100  cells,  and  the  electro-motive  force  of  each  element 


APPENDIX    AND   NOTES.  125 

of  this  battery  be  such  as  to  produce  a  difference  in 
tension  between  its  plates  equal  to  1,  the  difference 
between  its  poles  or  end  plates  will  be  equal  to  100. 
But  it  must  be  understood  that  degrees  of  tension  are 
only  relative  or  comparative.  The  earth  being  our 
great  reservoir  of  electricity,  its  tension  is  called  zero, 
and  it  affords  us  a  convenient  standard  of  reference  in 
comparing  other  tensions,  but  even  the  absolute  tension 
of  the  earth  sometimes  varies  in  different  times  and 
places. 

Suppose  we  take  the  battery  of  100  cells  above 
referred  to,  place  it  upon  a  well-insulated  stand,  and  con- 
nect one  pole  of  it,  say  the  zinc  or  negative  pole,  to 
earth,  and  leave  the  other  pole  disconnected,  and  there- 
fore insulated  by  the  air.  The  end  which  is  connected 
with  the  earth  being  in  free  communication  with  it, -will 
now  have  a  tension  of  zero,  and  the  opposite  end  of  the 
battery  will  have  a  tension  of  100  positive,  or  above 
that  of  the  earth,  and  if  a  wire  were  connected  from  it 
to  the  earth  a  powerful  current  of  electricity  will  pass 
between  them. 

If  now  the  copper  or  positive  pole  be  placed  to  the 
earth,  and  the  zinc  pole  insulated,  the  tension  of  the 
former  will  now  be  zero,  and  that  of  the  latter  100 
negative,  or  below  that  of  the  earth.  In  each  of  these 
cases  the  degree  of  tension  is  the  same,  but  in  one  case 
it  is  above  that  of  the  earth,  or  positive,  and  in  the  other 
case  below  that  of  the  earth,  or  negative. 

If  the  zinc  or  negative  pole  of  the  same  battery  be 
now  connected  to  the  earth,  and  the  positive  pole,  in- 
stead of  being  left  free,  is  connected  by  a  short  and 
thick  wire,  of  no  appreciable  resistance,  to  the  negative 
pole,  the  tensions  throughout  the  circuit  will  be 
materially  changed,  although  the  electro-motive  force 
will  remain  unaltered.  The  tension  at  the  copper 
pole  of  the  battery,  which  was  1,000  when  the  pole  was 
entirely  disconnected,  now  becomes  the  same  as  that 
of  the  earth,  or  at  least  but  very  little  above  it.  If  a 
wire  offering  considerable  resistance  be  substituted  for 


126  APPENDIX    AND    NOTES. 

the  short  and  thick  wire  which  connects  0  and  Z,  the 
tension  at  C  will  be  raised,  although  that  of  Z  will  still 
be  kept  at  zero  by  its  connection  with  the  earth  at  that 
point.  In  proportion  as  the  resistance  of  this  connect- 
ing wire  is  increased,  the  tension  at  C  rises  until,  when 
the  resistance  becomes  infinite,  the  tension  will  again 
reach  100,  for  infinite  resistance  is  absolute  insulation. 
The  tension  is  now  equal  to  the  electro-motive  force, 
but  it  is  obvious  that  it  can  never  exceed  it  under  any 
circumstances. 

If  a  battery  of  100  cells  is  connected  to  a  telegraph 
line  of  100  miles  in  length,  whose  insulation  is  perfect, 
and  which  is  not  connected  to  the  earth  at  the  remote 
end,  the  line  will  instantly  acquire  a  tension  of  100 
throughout  its  whole  length  (this  being  equal  to  the 
electro-motive  force  of  the  battery),  and  this  would  oc- 
cur if  the  wire  were  a  thousand  or  a  million  times  that 
length.  After  the  line  has  acquired  the  same  tension 
as  the  pole  of  the  battery  to  which  it  is  attached,  no 
current  will  flow  from  the  battery. 

If  the  distant  end  of  the  line  is  connected  to  the 
earth,  the  battery  will  come  into  action,  and  a  current 
of  electricity  will  pass  through  it.  This  will  at  once 
change  the  tensions  throughout  the  whole  line.  The 
distant  end  of  the  line,  which  originally  had  a  tension 
of  100,  will  now  have  a  tension  of  zero,  being  con- 
nected directly  to  the  earth,  and  from  this  point  the 
tension  will  rise  gradually  and  regularly  along  the 
whole  length  of  the  line  to  the  pole  of  the  battery. 
So  also  the  tensions  within  the  cells  of  the  battery 
itself  follow  the  same  law. 

The  relation  existing  in  a  voltaic  circuit  between  the 
resistances,  electro-motive  forces,  and  tensions,  may  be 
graphically  and  accurately  represented  to  the  eye  by  a 
geometrical  projection  based  upon  mathematical  reason- 
ing, a  method  first  suggested  by  Ohm,  and  more 
recently  elaborated  by  Mr.  F.  C.  Webb,  and  which  he 
explains  as  follows : 

Let  all  the  parts  of  a  circuit;  whether  liquid  or  solid, 


APPENDIX    AND    NOTES.  127 

be  expressed  in  their  successive  order  by  portions  of  a 
continuous  horizontal  line,  which  shall  be  to  one  another 
as  the  reduced  lengths  or  resistances  of  those  parts. 
Let  the  tension  at  any  given  point  in  the  circuit  be 
represented  by  the  perpendicular  height  of  a  point 
above,  or  depth  below,  the  horizontal  line  representing 
the  resistances.  This  when  above  the  line  will  indi- 
cate a  positive,  and  when  below,  a  negative  tension. 
The  horizontal  line  of  resistances  may  be  termed  the 
axis. 

In  order  to  represent  the  tension  at  every  point  in 
the  circuit,  we  must  construct  a  line  termed  the  line  of 
tension.  The  perpendicular  height  of  this  line  above 
the  axis  at  any  point,  indicates  a  corresponding  positive 
tension  at  that  point,  and  its  depth  below  in  the  same 
manner  indicates  a  negative  tension.  When  this  line 
crosses  the  axis  the  point  of  intersection  has  no  tension. 

Electro-motive  force  consists  in  a  sudden  and  con- 
stant difference  in  the  tension  of  the  points  situated 
immediately  upon  opposite  sides  of  the  surface  of 
junction  between  the  zinc  element  and  the  liquid  of 
the  battery.  The  electro-motive  forces  in  the  circuit 
must,  therefore,  be  represented  by  a  sudden  rise  in  the 
line  of  tension  at  the  points  along  the  axis  at  which 
they  occur,  thus  forming  lines  perpendicular  to  the 
axis.  The  magnitude  of  these  lines  must  be  propor- 
tional to  the  electro  -  motive  force  they  represent. 
Moreover,  as  the  electro-motive  force  is  a  quantity 
depending  solely  upon  the  nature  of  the  elements  at 
the  surface  of  junction  at  which  it  occurs,  and  not  at 
all  on  any  change  in  the  resistance  or  electrical  state 
of  the  circuit,  these  perpendicular  lines  constantly 
maintain  the  same  magnitude,  although  their  posi- 
tion as  regards  the  axis  may  be  altered  in  various 
ways. 

Now  let  us  construct  a  diagram  which  shall  correctly 
represent  the  electro-motive  forces,  tensions,  resist- 
ances, and  strength  of  current,  as  a  telegraph  line  with 
a  closed  circuit,  having  a  battery  of  three  cells  at  each 


128  APPENDIX   AND    NOTES. 

end  of  the  line,  which  will  be  a  sufficient  number  to 
correctly  represent  the  arrangement  of  the  circuit  or- 
dinarily used  on  American  telegraph  lines. 


Let  the  horizontal  line  N  P'  (see  Fig.  59)  represent 
the  axis,  or  line  of  resistances,  the  latter  being  repre- 
sented in  their  respective  order,  beginning  at  the  point 
of  contact,  N,  between  the  extreme  zinc  plate  of  the 
battery  and  the  liquid  of  the  cell.  N  B,  B  C,  and  C 
P  represent  the  respective  internal  resistances  of  the 
three  battery  cells,  and  N  P  that  of  the  entire  battery. 
Let  P  H  N'  represent  the  resistance  of  the  line  wire, 
and  N'  P'  that  of  the  battery  at  the  opposite  end  of 
the  line.  Erect  a  perpendicular,  N  E,  at  the  point  N, 
and  divide  it  into  three  portions,  N  F,  F  Of,  and  G  E, 
which  shall  be  to  each  other  as  the  electro-motive 
forces  at  N,  B,  and  C.  The  other  battery,  N'  P',  having 
its  negative  pole,  N',  to  the  line,  will  give  a  negative 
tension;  therefore  a  perpendicular  P'  E'  let  fall  below 
the  axis  from  the  point  P,  and  divided  in  the  same 
manner,  will  represent  the  electro-motive  forces  of  the 
battery  N'  P'.  Therefore  the  line  N  P'  represents  the 
sum  of  all  the  resistances,  and  N"  E  +  P'  E'  the  sum  of 
the  electro-motive  forces.  It  necessarily  follows 
that  the  line  of  tension,  M  H  M',  which  we  get  by 
joining  E  and  E',  varies  in  the  angle  of  its  inclination 
to  the  axis  according  to  the  proportion  between  the 
sum  of  the  electro-motive  forces,  N"  E  and  P'  E',  and 


APPENDIX    AND    NOTES. 


129 


the  sum  of  the  resistances,  N  P';  and  the  degree  of  its 
inclination  will  therefore  accurately  represent  the 
effective  working  strength  of  the  current  in  all  parts  of 
the  circuit. 

The  varying  tensions  within  the  battery  maybe  cor- 
rectly represented  as  follows  :  Having  joined  JEand  E', 
erect  perpendiculars  at  B  and  C  and  P.  Now  as  the 
effective  strength  of  current,  represented  by  the  incli- 
nation of  the  line  E  E',  is  the  same  at  every  point 
throughout  the  whole  circuit,  draw  F  I  parallel  to  E  E'. 
Then  F  I  will  be  the  line  of  tension  in  the  first  cell, 
falling  regularly  through  the  resistance  of  the  liquid  to 
the  surface  of  generation,  B,  of  the  second  zinc,  where 
it  rises  suddenly  to  the  extent  of  the  electro-motive 
force  there  situated.  Draw  Gr  K  parallel  to  E  E',  inter- 
secting B  0  at  J.  I  J  will  then  be  equal  to  F  Gr, 
which  represents  the  electro-motive  force  at  B,  and  J  K 
will  be  the  line  of  tension  in  tne  second  cell.  Now  as 
G  K  is  parallel  to  E  E',  K  L  will  be  equal  to  Gr  E,  the 
electro-motive  force  at  C,  and  L  M  will  be  the  line  of 
tension  in  the  third  cell.  In  the  same  manner  the  line 
of  tension  within  the  other  battery  N  P'. 

The  terminal  points  of  the  line  N  and  P',  being  con- 
nected directly  with  the  earth,  their  tension  will  be 
equal,  and  the  same  as  that  of  the  earth,  which  is 
assumed  to  be  zero  ;  that  is,  neither  positive  nor  neg- 
ative. It  is  manifest  that  at  the  point  II,  midway  of 
the  circuit  where  the  line  of  tension  crosses  the  axis, 
the  tension  is  the  same  as  that  of  the  earth,  or  zero. 

In  the  illustration  given,  the  line  is  supposed  to  be 
in  a  condition  of  perfect  insulation.  In  actual  practice 
there  isaleakage  at  every  support  throughout  the  whole 
length  of  the  circuit.  The  line  of  tension  in  this  case 
would  form  a  double  catenary  curve,  its  angle  of  incli- 
nation to  the  axis  constantly  increasing  from  H  to  M 
and  M',  because  in  an  imperfectly  insulated  or  leaky 
line  the  current  continually  increases  in  strength  in  each 
direction  from  the  neutral  point  to  the  battery  poles 
atP  andN'. 


130  APPENDIX    AN'D    NOTES. 

Mr.  Webb  has  demonstrated  the  correctness  of  the 

",    above  method  of  geometrical  projection  by  applying 

»    Ohm's  formula  for  obtaining  the  tension  at  any  point 

\  of  the  circuit.     The  results  are  found  to  correspond  in 

every  case.     This  formula  may  bo  stated  as  follows  : 

Let  T  =  the  tension  at  any  given  point  of  the  circuit  a;. 

Y  =  the  abscissa  of  that  point  y,  taking  as  origin  the  point  of 

least  tension. 

A  =  (he  sum  of  the  electro-motive  forces. 
L  =  the  reduced  leugth  or  resistance  of  the  entire  circuit. 
O  =  the  sum  of  the  electro-motivo  forces  included  in  Y. 
C  =  the  tension  of  the  whole  circuit  to  external  objects.     That 

is  to  say,  the  tension  of  the  circuit,  if  it  be  an  insulated 

circuit,  uud  electrified  by  a  source  not  contained  within 

it. 

Then  T  ==  ~  Y  -  0  +  C. 

J_J 

As,  in  the  case  under  consideration,  the  earth  forms 
part  of  the  circuit,  the  constant  C  disappears  and  the 
formula  becomes 


Now  take  a  point  x  in  the  diagram,  and  the  tension 
x  x'  will  be  found  to  agree  with  the  formula. 

The  quantities  in  the  formula  are  thus  represented 
geometrically  in  the  figure  : 

A  =  NE 

O  =  x'  x" 
T^xx' 

Now  since  the  triangles  H  N  E  and  H  x  x"  are  sim- 
ilar, we  have 

N  H  :  N  E  :  :  n  x  \  xx" 

Consqnently  x  x"  =  ^-7,  H  x, 
.M  H 

and  J  K  being  parallel  to  0  L,  we  have 

a'  x"  =  K  L. 
But  x  x  =  x  x"  -  x'  x"  ; 

Therefore  xx'  =  ^-r.  H  X  -  x"  x", 

Or,  T  =  £  Y  -  O. 

L 


APPENDIX    AN1>   NOTES. 


131 


An  experimental  proof  of  the  above  theory  of  ten- 
sion may  be  obtained  by  connecting  a  wire  from  the 
neutral  point  in  the  middle  of 'the  closed  circuit  of- a 
telegraph  line,  and  inserting  a  galvanometer  or  relay. 
It  will  be  found  that  no  current  passes  between  •  the 
line  and  the  earth,  which  proves  that  the  electric  ten- 
sion or  potential  at  that  point  is  zero,  or  the  same  as, 
that  of  the  earth  itself. 

170.  DOUBLE  TRANSMISSION. — One  of  the  most  inte- 
resting problems  in  practical  telegraphy  is  that  of  double 
transmission,  or  working  in  opposite  directions  at  the 
same  time  over  a  single  wire.  This  apparently  para- 
doxical result  may  be  accomplished  in  several  different 
ways,  the  principles  involved  being  very  simple  arid 
easily  understood.  The  method  shown  in  the  accom-; 
paiiying  diagram  is  that  of  Siemens  &  Halske,  of  Ber- 
lin, Prussia ;  the  apparatus  now  used  in  this  country 
differing  slightly  from  it  in  some  of  its  minor  details. 


Fia. 


A  and  B  (Fig.  60),  are  the  two  terminal  stations  of 
the  line.  The  main  battery  E,  at  station  A,  is  placed 
with  its  -f ,  and  the  battery  E'  at  station  B  with  its  — 


132  APPENDIZ    AND    NOTES.  ) 

pole  to  the  line,  as  represented.  M  and  M'  are  the 
receiving  magnets  or  relays,  which  are  wound  through- 
out with  two  similar  wires  of  equal  length,  as  shown  in 
the  figure,  whose  connections  will  hereafter  be  explained. 
The  rheostat  or  resistance,  X,  must  be  adjusted  so  as  to 
be  exactly  equal  to  that  of  the  line  A,  B,  added  to  that 
of  the  relay  wire  7,  5,  at  the  other  station.  Similarly 
X'  is  also  made  equal  to  the  line  including  the  relay 
wire  3,  1. 

If,  now,  the  key  K  at  station  A  be  depressed,  the 
current  from  the  battery  E  will  divide  at  the  point  1, 
one  portion  going  through  the  relay  coils  to  3,  over  the 
line  A,  B  to  7,  and  thence  through  the  relay  M'  to  5, 
key  lever  6'.  and  contact  C'  to  the  earth  at  G',  and  the 
other  portion  in  an  opposite  direction  through  the  relay 
coils  from  2  to  4,  and  thence  through  the  resistance  X 
to  the  negative  pole  of  the  batter}7.  These  two  cur- 
rents will  be  equal  to  each  other,  the  resistance  being 
the  same  by  each  of  the  two  routes,  as  before  explained, 
but  as  they  pass  in  opposite  directions  through  tb.o  two 
wires  surrounding  the  relay  M,  they  produce  no  mag- 
netic effect  upon  it.  The  relay  at  B,  however,  will  be 
affected  by  the  current  coming  from  A  through  the 
wire  7,  5,  and  will  give  signals  corresponding  to  the 
movements  of  the  key  at  that  station. 

If,  now,  the  key  at  B  be  also  depressed,  the  same 
action  takes  place  ;  one  half  the  current  passes  over 
the  line,  combining  with  the  current  from  A,  and  the 
other  half  returns  to  the  battery  through  the  other 
Wire  of  the  relay  and  the  rheostat. 

The  relay  wires  1,  3  and  7,  5  are  now  traversed  by 
the  double  current,  equal  to  5  +  5,  but  the  wires  2,  4 
and  6,  8  are  traversed  only  by  the  current  of  a  single 
battery,  having  at  A  the  force  of  £  and  at  B  the  force  of 
j.  The  latter  current  being  in  the  opposite  direction  to 
the  former,  the  relays  at  both  stations  are  affected  by 
the  difference  in  the  forces  of  these  currents,  the  relay 
at  A  by  (J+J)  -  J,  and  the  relay  at  B  by  (J+5)  -  §. 


MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH.  133 

Thus  each  station  receives  its  signal  through  the  action 
of  the  distant  battery  only. 

In  the  arrangement  shown  in  figure  60  a  third  posi- 
tion occurs,  where  one  of  the  keys,  at  B  for  instance, 
is  in  the  act  of  changing  from  the  front  contact  A'  to 
the  rear  contact  C',  or  vice  versa,  in  which  case  the  cur- 
rent from  A  is  interrupted  at  B',  and  therefore  passes 
through  the  second  wire  of  the  relay  6,  8,  but  this  time 
in  the  same  direction,  and  thence  through  the  rheostat 
X'  to  the  ground.  The  current  arriving  at  B  is  con- 
siderably weakened  in  consequence  of  the  additional 
resistance  encountered  at  X',  but  this  is  compensated 
for  by  its  passing  through  both  wires  of  the  relay  M  in 
the  same  direction,  and  its  action  upon  the  relay,  there- 
fore, remains  about  the  same  as  before. 

One  slight  difficulty,  however,  arises  in  this  connec- 
tion. It  will  be  seen  that  when  the  current  at  the 
receiving  station  is  thus  momentarily  thrown  through 
both  relay  wires  and  the  rheostat,  it  must  necessarily 
cause  an  unequal  division  of  the  current  between  the 
two  opposing  relay  wires  at  the  sending  station,  as  the 
resistance  of  the  long  circuit  becomes  about  double  that 
of  the  short  one.  This  effect  is  avoided  in  the  Ameri- 
can system  by  a  modification  of  the  transmitting  appa- 
ratus, which  is  operated  by  the  lever  of  a  sounder  placed 
in  a  local  circuit  in  connection  with  the  key.  When 
the  local  circuit  is  closed  the  downward  movement  of 
the  sounder  lever  makes  the  battery  connection  upon 
a  flat  spring,  and  the  movements  thus  imparted  to  the 
spring  breaks  the  earth  contact.  The  spring  being  at- 
tached to  the  line  wire  the  connection  is  necessarily 
always  complete,  either  direct  or  through  the  battery, 
and  it  is  not  obliged  to  pass  through  the  rheostat  when 
the  transmitter  is  changing  from  the  battery  to  the  earth 
contact,  or  vice  versa.  The  disadvantage  in  this  case 
arises  from  the  fact  that  the  main  battery  is  thrown  on 
short  circuit  at  each  movement  of  the  transmitter,  ren- 
dering it  necessary  to  interpose  a  considerable  addi- 
tional resistance  between  the  back  contact  and  the  bat- 


134  APPENDIX    AND    NOTES.        V'   = 

tery,  to  prevent  the  rapid  consumption  of  the  latter 
which  would  otherwise  ensue.  These  improvements 
"were  devised  by  Mr.  J.  B.  Stearns. 

In  working  this  system,  it  is  necessary  to  keep  the 
rheostat  so  adjusted  that  its  resistance  will  correspond 
exactly  with  that  of  the  line,  as  above  shown.  If  the 
relay  works  too  feebly  the  counter  current  must  be 
weakened  by  increasing  the  resistance  of  the  rheostat. 
If  the  magnetism  is  too  strong  the  resistance  should  be 
diminished.  A  careful  study  of  the  diagram  will  show 
that  this  system  operates  equally  well,  whether  similar 
or  opposite  poles  of  the  two  batteries  are  placed  to- 
wards the  line.  With  like  poles  the  action  will  be  as 
follows: 

If  the  key  at  A  be  depressed,  the  current  on  the 
line  will  be  \  and  through  the  rheostat  £,  neutralizing 
each  other  upon  the  relay  of  A,  but  giving  a  current 
of  g  in  the  relay  at  B.  Now,  if  the  key  at  B  be  also 
depressed,  a  current  equal  to  f  is  thrown  through  each 
wire  of  his  relay,  but  the  current  £  being  equal  and 
opposite  to  §  the  current  of  the  main  line  will  —  0. 

The  current  through  the  second  wire  of  the  relays 
being  still  unaffected,  each  relay  will  give  a  signal  cor- 
responding to  the  time  the  key  at  the  other  station  is 
depressed. 

171.  EDISON'S  BUTTON  REPEATER. — This  is  a  very 
simple  and  ingenious  arrangement  of  connections  for  a 
button  repeater,  which  has  been  found  to  work  well  in 
practice.  It  will  often  be  found  very  convenient  in 
cases  where  it  is  required  to  fit  up  a  repeater  in  an 
emergency,  with  the  ordinary  instruments  used  in 
every  office.  Fig.  61  is  a  plan  of  the  apparatus. 

M  is  the  western  and  M'  the  eastern  relay.  E  is  the 
main  battery,  which,  with  its  ground  connection  G,  is 
common  to  both  lines.  E'  is  the  local  battery,  and  L 
the  sounder.  S  is  a  common  "  ground  switch,"  turn- 
ing on  two  points,  2  and  3.  In  the  diagram  the  switch 
is  turned  to  2,  and  the  eastern  relay,  therefore,  repeats 
into  the  western  circuit,  while  the  western  relay  ope- 


MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 


135 


rates  the  sounder,  the  circuit  between  1  and  2  through 

the  sounder  and  local  battery  being  common  to  both 

the  main  and  local  currents.     If  the  western  operator 

e  breaks  the  relay 

WEST  1 

E  -S- 


M  opens,  and  con- 


sequently the  soun< 
dcr,  L,  ceases  tp 
work.  The  opera- 
tor in  charge  then 
turns  the  switch  to 
3,  and  the  reverse 
operation  takes 
place;  the  westera 
relay  repeats  into 
the  eastern  circuit, 
and  the  eastern 
relay  operates  the 
sounder.  The  soun- 
der being  of  coarse  wire,  offers  but  a  slight  resistance  to 
the  passage  of  the  main  current. 

172.  BRADLEY'S  TANGENT  GALVANOMETER. — The  com^ 
mon  galvanometer  used  for  the  measurement  of  elec- 
tric currents  consists  of  a  magnetized  steel  needle, 
suspended  in  the  centre  of  a  hollow  frame  covered  with 
insulated  copper  wire.  The  degree  of  deflection  of  this 
needle  from  its  normal  position  in  the  magnetic  meridian, 
when  a  current  is  passing,  indicates  the  strength  of  the 
current.  In  the  ordinary  galvanometer,  however,  the 
angle  through  which  the  needle  is  moved,  or  in  other 
words,  the  number  of  degrees  over  which  it  passes,  is  not 
.an  accurate  measure  of  the  strength  of  the  current  when 
the  deflection  exceeds  15°,  for  the  further  the  needle 
moves  from  a  position  parallel  to  the  wires  of  the  coil 
the  more  nearly  does  it  approach  a  right  angle,  in  whicji 
position  the  effect  is  null,  so  that  the  action  of  the  cur- 
rent upon  it  becomes  less  and  less  powerful  as  the  de- 
viation increases.  Several  arrangements  have  been 
tried  in  order  to  obviate  this  objection,  the  most  com- 
mon being  that  of  a  ring  having  a  groove  on  its  edge 


APPENDIX   AND   NOTES. 


filled  with  wire.  The  needle  is  hung  precisely  in  the 
centre  of  the  ring,  and  must  not  be  longer  than  one 
sixth  of  its  diameter  —  a  half  inch  needle  requiring  a 
three  inch  ring.  The  needle  is  then  deflected  with  a 
force  varying  as  the  tangent  of  the  number  of  degrees 
through  which  the  needle  moves.  Owing  to  the  great 
distance  of  the  coil  from  the  needle,  this  arrangement 
has  very  little  sensitiveness  compared  with  the  common 
galvanometer. 

In  Bradley  's  Galvanometer  a  compound  needle  is 
employed,  composed  of  several  needles  of  thin,  flat 
steel,  fixed  horizontally  upon  a  light  flat  ring  of  metal, 
forming  a  complete  circular  disc  of  needles,  having  an 
agate  cup  in  the  centre,  to  rest  upon  the  pivot  upon 
which  it  moves.  At  each  extremity  of  the  meridian 
light  points  project,  to  indicate  the  degrees  of  deflection. 
This  compound  needle,  after  having  been  magnetized, 
is  placed  within  or  over  a  coil  whose  breadth  is  exactly 
equal  to  the  diameter  of  the  disc.  This  compound  cir- 
cular needle,  being  under  the  influence  of  the  same 
number  of  convolutions  of  the  coil  in  all  its  deflections, 
fulfils  the  required  conditions  for  a  true  tangent  gal- 
vanometer. 

The  theorem,  "  The  intensity  of  currents,  as  measured 
by  the  tangent  galvanometer,  is  proportional  to  the  tangents 
of  the  angles  of  deflection"  may  be  verified  in  the  fol- 
lowing manner  : 

Call  the  terrestrial  magnetism,  whose  tendency  is  to  di- 
rect the  galvanometer  needle  to  the  magnetic  meridian, 
the  unit  of  directive  force,  and  let  this  unit  be  represented 
geometrically  by  the  line  A  M  (Fig  62),  which  is  the 
radius  of  the  circle  M  B  M  —  the  line  M  A  M  representing 
the  meridian.  When  there  is  no  other  force  acting  on  the 
needle  its  direction  is  with  the  meridian.  Now  let  an 
electric  current  be  sent  through  the  galvanometer  coil, 
whose  directive  force  is  precisely  equal  to  the  terrestrial 
force,  and  whose  tendency  is  to  direct  the  needle  in 
a  line  perpendicular  to  the  meridian,  and  let  this  force 
be  represented  by  the  line  A  B. 


MODERN  PRACTICK  OP  TUB  ELECTRIC  TELEGRAPH. 


137 


If  the  terrestrial  force  could  now,  for  a  moment,  be 
suspended,  the  needle  would  point  due  east  and  west ; 

but  the  combined  action  of 
the  two  equal  forces  will 
direct  the  needle  toward 
the  point  of  intersection  of 
the  line  drawn  perpendic- 
ularly from  M,  and  that 
drawn  horizontally  from  B, 
at  1,  which  direction  cuts 
the  quadrant  at  45°,  the  line 
M  1  being  the  tangent  of 
45°,  which  is  1. 

Now,  if  we  augment  the 
intensity  of  the  current 
through  the  coil  to  twice 
its  present  force,  which  will 
be  2,  and  will  be  represen- 
ted by  the  line  A  C,  the 
combined  forces  A  M  and 
A  C  will  direct  the  needle 
toward  the  point  2.  If  we 
now  lay  a  protractor  on  the 
circle,  we  find  that  the  line  A  2  cuts  it  about  63°  30',  of 
which  the  tangent  is  2. 

We  may  increase  the  parallelogram  erected  upon  A 
M  at  pleasure,  and  the  two  forces  combined  will 
always  so  balance  the  needle  between  them  as  to  make 
it  point  from  A,  diagonally,  across  the  parallelogram 
to  its  opposite  angle,  the  height  of  which  is  the  tangent 
of  the  angle  of  deflection. 

By  inspection  of  the  diagram  it  is  seen  that  the  law 
holds  good  in  the  subdivisions  of  the  force  A  B,  as  at 
.5  .25  and  .125,  a  truth  admitted  by  all  experimenters, 
as  to  the  relations,  up  to  14°. 

173.  THOMPSON'S  REFLECTING  GALVANOMETER. — This 
is  the  most  delicate  apparatus  of  this  kind  which  has 
yet  been  devised,  and  is  for  this  reason  employed  in 
operating  the  Atlantic  Cables. 


FIG.  62. 


138  APPENDIX   AND   NOTES. 

The  special  feature  which  distinguishes  this  galvan- 
ometer from  an  ordinary  one,  is  the  extreme  lightness 
of  the  magnet  or  needle,  and  the  delicacy  with  which 
it  is  suspended  in  a  horizontal  position.  Instead  of  an 
index  needle,  to  render  the  motions  of  the  magnet  visi- 
ble to  the  eye,  a  reflected  ray  of  light  is  made  use  of, 
which,  of  course,  can  be  made  of  any  required  length. 
This  arrangement  is  of  great  practical  value  in  mea- 
suring faint  electrical  currents,  too  feeble  to  be  indicated 
by  any  other  apparatus.  It  is  especially  valuable  in 
submarine  telegraphing,  because  it  permits  the  use  of 
such  extremely  low  battery  power. 

When  the  insulation  of  a  cable  is  in  the  slightest 
degree  defective  at  any  point,  a  current  of  intensity 
has  a  tendency  to  aggravate  the  fault,  and  to  corrode 
and  eat  away  the  conductor  by  chemical  decomposi- 
tion, at  the  point  where  the  escape  occurs,  finally  des- 
troying the  communication  altogether. 

Fig.  63  is  a  side  elevation  of  this  instrument,  show- 
ing a  section  through  the  galvanometer  coils  and  the 
outer  case  containing  them.  Fig.  64  is  a  cross  section 
through  the  coils,  showing  the  magnet,  technically 
termed  the  needle.  Similar  letters  refer  to  like  parts 
in  both  figures.  The  magnet  A  is  a  small  bar  of  steel, 
one  half  inch  in  length  and  one  tenth  of  an  inch  square, 
cemented  to  the  back  of  a  very  thin  circular  glass  mir- 
ror, a.  The  mirror  is  suspended  in  a  brass  frame,  B 
(Fig.  64),  by  an  exceedingly  delicate  silk  fibre,  and  is 
adjusted  in  height  by  the  screw  b.  This  frame  slides 
into  a  vertical  groove  left  in  the  centre  of  the  coil, 
dividing  it  into  two  parts.  The  coil  and  mirror  are 
enclosed  in  the  brass  case  D,  this  case  having  pieces  of 
glass  let  in  wherever  necessary,  to  permit  the  passage 
of  light.  The  object  of  this  arrangement  is  to  pre- 
vent the  mirror  and  its  attached  needle  from  being  dis- 
turbed by  currents  of  air. 

A  narrow  pencil  of  luminous  rays  from  the  lamp,  E, 
passes  through  the  opening,  F,  which  is  capable  of  ad- 
justment by  the  slide  G-.  This  pencil  of  light,  passing 


MODERN    PRACTICE    OF   THE    ELECTRIC    TELEGRAPH. 


139 


through  the  lens,  is  reflected  by  the  mirror  back  through 
the  lens  upon  an  ivory  scale  at  I,  as  shown  by  the  dot- 
ted lines.  The  scale  is  horizontal,  extending  to  the 


right  and  left  of  the  centre  of  the  instrument,  the  zero 
point  being  exactly  opposite  the  lens.  The  luminous 
pencil  is  brought  to  a  sharp  focus  upon  the  scale  by  a 


|40  APPENDIX   AND    NOTES. 

sliding  adjustment  of  the  lens  M,  in  the  tube  N.  When 
the  needle  is  at  rest  in  its  normal  position,  and  no  cur- 
rent is  passing,  the  spot  of  light  which  serves  as  an  in- 
dex will  remain  at  zero  on  the  scale. 

The  operator  reads  the  signals  from  a  point  just  in 
the  rear  of  the  magnet  and  coils,  the  light  of  the  lamp 
being  cut  off  by  the  screen  Y,  so  that  he  only  sees  the 
small  luminous  slit  through  which  the  light  enters  the 
instrument,  and  a  brilliantly  denned  image  of  the  slit 
upon  the  white  ivory  scale  just  above,  which  is  kept  in 
deep  shadow  by  the  screen  Y.  A  very  minute  dis- 
placement of  the  magnet  gives  a  very  large  movement 
of  the  ray  of  light  on  the  scale  I,  the  angular  dis- 
placement of  the  ray  of  light  being  double  that  of  the 
needle. 

It  is  obvious  that  the  ray  of  light  from  the  needle 
will  be  reflected  to  the  right  or  left  of  zero  on  the  scale, 
according  as  the  deflection  is  produced  by  a  positive  or 
negative  current.  The  Morse  alphabet  is  used  for  sig- 
naling through  the  Atlantic  cable,  deflections  on  one 
side  of  zero  indicating  dots,  and  on  the  other  side 
dashes. 

It  will  be  observed  that  the  end,  and  not  the  broad 
part  of  the  flame  of  the  lamp,  is  presented  to  the  slit 
F,  which  is  also  arranged  to  receive  the  brighest  part  of 
the  vertical  section  of  the  flame. 

The  galvanometer  coils,  E,  consist  of  many  thousand 
convolutions  of  fine  insulated  copper  wire,  arid  they 
are  insulated  from  the  case,  D,  by  a  disc  of  hard  rub- 
ber, T,  to  which  they  are  fastened. 

The  instrument  is  usually  provided  with  a  directing 
magnet,  by  which  its  sensitiveness  may  be  varied  to  a 
great  extent.  This  magnet  is  in  the  form  of  a  bar, 
slightly  curved,  and  is  of  considerable  power.  It  is 
placed  upon  a  vertical  rod  passing  through  its  centre, 
which  is  fixed  above  the  coil  immediately  over  the 
needle,  in  such  a  manner  that  it  can  be  turned  horizon- 
tally so  as  to  follow  the  movements  of  the  needle,  or 
be  removed  nearer  to  or  further  from  it  vertically.  If 


MODERN    PRACTICE    OF   THE    ELECTRIC   TELEGRAPH.  141 

it  is  placed  with  its  south  pole  over  the  north  pole  of 
the  needle,  it  will  add  its  directive  force  to  that  of  the 
earth,  and  by  holding  the  needle  more  powerfully  in 
its  position,  will  lessen  its  sensitiveness.  The  nearer 
the  magnet  approaches  the  needle  the  greater  will  be 
its  power  over  it,  and  it  can  be  arranged  so  as  to  hold 
the  needle  in  any  desired  position.  If  it  is  placed  in  a 
reverse  direction,  so  as  to  repel  the  needle  instead  of 
attracting  it,  it  will  lessen  the  attractive  force  of  the 
earth  so  as  to  increase  its  sensitiveness,  and  in  a  cer- 
tain position  will  render  the  galvanometer  astatic. 
When  the  magnet  is  too  near  the  needle  it  repels  to 
the  full  extent  of  the  scale.  If  it  is  raised  upon  the 
supporting  rod  the  repelling  effect  will  decrease,  until, 
at  a  certain  distance  from  the  magnet,  the  spot  of  light  on 
the  scale  can  be  held  at  zero.  The  greatest  sensibility 
is  obtained  at  the  point  at  which  the  slightest  lowering 
of  the  magnet  upon  the  rod  will  again  repel  the  needle 
to  the  full  extent  of  its  swing. 

An  improvement  in  this  instrument,  made  by  Mr.  C. 
F.  Varley,  consists  in  giving  the  mirror  a  concave  form, 
silvered  upon  the  back,  and  thus  dispensing  with  the 
use  of  the  lens  above  described. 

174.  MODE  OF  WORKING  TOE  ATLANTIC  CABLES. — • 
Yery  little  has  been  made  public  in  regard  to  the  pre- 
cise method  employed  in  signaling  through  the  Atlantic 
cables.  As  before  remarked,  the  reflecting  galvanome- 
ter is  employed  as  a  receiving  instrument,  and  by  em- 
ploying deflections  on  one  side  of  zero  to  represent 
dashes,  and  those  on  the  other  side  dots,  the  Morse 
alphabet  is  found  to  answer  the  purpose  admirably.  It 
is  said  that  the  two  cables  have  been  looped  in  a  metallic 
circuit  without  ground  connection,  arid  that  they  have 
also  been  worked  separately  witlr  and  without  conden- 
sers. The  latter  method  is  made  use  of  in  order  to 
avoid  the  disturbances  generated  by  what  arc  known 
as  "  earth  currents." 

Different  parts  of  the  earth  and  sea  are  found  to  be 
at  different  electric  potentials.  One  part  is  electro- 


142  APPENDIX    AND   NOTES. 

positive  or  electro-negative  to  another.  That  is  to  saj*, 
there  is  the  same  difference  between  the  two  parts  of 
the  earth  that  exists  between  the  two  poles  of  a  bat- 
tery. If,  therefore,  these  two  points  are  joined  by  a 
wire,  a  current  will  flow  through  that  wire  as  if  from  a 
battery,  and  this  current  is  termed  an  earth  current,  to 
distinguish  it  from  the  current  generated  by  an  ordi- 
nary voltaic  battery.  This  difference  of  potential  be- 
tween two  given  points,  such  as  Newfoundland  and 
Valencia,  is  not  constant  but  continually  varies,  causing 
a  corresponding  variation  in  the  current  it  produces. 
This  current  and  its  fluctuations  interfere  with  the  sig- 
naling current,  disturbing  the  distinctness  of  the  sig- 
nals. When  very  rapid  changes  take  place  in  the  elec- 
tric condition  of  the  earth,  it  is  known  as  a  magnetic 
storm,  and  this  occasionally  interferes  with  the  work- 
ing of  all  telegraph  lines. 

By  the  method  of  working  with  condensers  the  dis- 
turbances from  this  cause  are  avoided.  The  condenser 
is  constructed  of  alternate  layers  of  tin  foil  and  thin 
plates  of  mica,  gutta-percha  or  paper,  saturated  with 
paraflBne,  arranged  like  the  leaves  of  an  interleaved 
book.  Each  alternate  metal  plate  is  connected  so  as  to 
form  two  distinct  series,  insulated  from  each  other,  one 
of  which  is  connected  with  the  line  and  the  other  with 
the  earth.  By  an  inductive  action,  similar  to  that  of 
the  well  known  Leyden  jar,  a  quantity  of  electricity, 
in  proportion  to  the  amount  of  surface  exposed,  may  be 
accummulated  or  stored  up  upon  the  metallic  plates.  If, 
therefore,  one  series  of  plates  be  charged  with  positive 
electricity  .the  other  series  will  become  negative  by 
induction,  and  by  means  of  this  induction  a  much 
larger  quantity  of  electricity  may  be  accumulated  than 
would  otherwise  be  the  case. 

The  manner  in  which  the  condenser  is  made  use  of  ia 
working  a  cable  is  as  follows : 

The  sending  apparatus  consists  of  a  battery,  B  (Fig. 
G5),  which  is  permanently  connected  with  the  cable 
through  the  back  contact  of  a  Morse  key,  K,  and  the 


MODERN    PRACTICE    OP   THE    ELECTRIC    TELEGRAPH. 


143 


CABLE 


cable  is  therefore  kept  constantly  charged  from  this 
batter}-.  When  the  key  is  depressed  the  cable  is 
placed  in  connection  with  the  earth  at  E.  The  receiv- 
ing apparatus  consists  of  the  reflecting  galvanometer 
G  (1G3),  one  terminal  of  which  is  attached  to  the  cable 
and  the  other  to  one  series  of  plates  in  the  condenser 

C — the  other  series 

|0 —  beingconnectcd  with 

the  earth,  as  shown 
in  the  figure.  R  is: 
a  very  high  resist- 
ance, inserted  in  a 
wire  leading  from 
the  point  0,  between 
the  cable  and  the 
galvanometer,  so  as 
to  allow  a  very  slight  but  constant  leakage  from  the 
cable  to  the  earth.  The  cable  is,  therefore,  charged  to 
the  tension  of  the  battery  B,  and  the  condenser  to  a 
tension  equal  to  that  of  the  point  0 — but  owing  to  the 
high  resistance  at  R  the  tensions  are  nearly  the  same. 
Upon  charging  the  cable  with  the  battery  at  K  a  charge 
of  electricity  enters  the  cable,  and  a  quantity  sufficient  to 
charge  the  condenser  passes  through  the  galvanometer, 
deflecting  the  mirror  until  the  condenser  is  charged 
equal  to  the  tension  of  the  point  0 — when  the  mirror 
will  return  to  zero.  By  putting  the  cable  to  earth  at 
K  a  portion  of  the  charge  will  be  withdrawn,  and  the 
tension  of  the  point  0  lowered  below  that  of  the  con- 
denser. A  portion  of  the  charge  of  the  latter,  there- 
fore, flows  into  the  cable,  deflecting  the  galvanometer  in 
the  opposite  direction.  The  right  and  left  hand  deflec- 
tions necessary  for  signaling  are  therefore  produced  with- 
out reversing  the  currents,  or  rendering  it  necessary  to 
entirely  discharge  tho  cable  after  each  signal.  This 
mode  of  signaling  possesses  many  important  advan- 
tages over  the  old  method,  in  point  of  rapidity  of  action 
and  freedom  from  interference  by  earth  currents.  The 
rate  of  working  through  the  cable  by  expert  operators 


144  APPENDIX    AND    NOTES. 

is  said  to  average  from  fifteen  to  twenty  words  per 
minute. 

175.  VELOCITY  OF  ELECTRIC  SIGNALS. — For  many 
years  the  velocity  of  electric  signals  in  passing  through 
a  conductor  was  supposed  to  be  infinitely  great,  or  at 
least  so  great  as  to  be  incapable  of  measurement.  In 
1849,  Professor  Sears  C.  Walker,  of  the  United  States 
Coast  Survey  service,  while  engaged  in  measuring 
longitude  by  means  of  the  electric  telegraph,  discovered 
a  perceptible  retardation.  Experiments  between  Wash- 
ington and  St.  Louis  indicated  a  velocity  not  far  from 
16,000  miles  per  second.  Some  of  the  measurements 
were  as  low  as  11,000  miles  per  second.  On  the  even- 
ing of  the  28th  of  February,  1868,  a  number  of  experi- 
ments were  made  by  the  officers  of  the  Coast  Survey, 
for  the  purpose  of  determining  accurately  the  difference 
in  longitude  between  Cambridge,  Mass.,  and  Sari  Fran- 
cisco, Cal.  A  wire  was  connected  from  Cambridge  to 
San  Francisco  and  back,  embracing  thirteen  repeaters — 
the  whole  distance  thus  traversed  by  the  signals  being 
about  7,000  miles. 

The  following  table  shows  the  time,  in  hundredths  of 
a  second,  occupied  by  a  signal  in  passing  from  Cam- 
bridge to  each  of  the  repeating  stations  and  back.  The 
number  of  repeaters  in  circuit  is  also  given : 

TIME    OF    TRANSMISSION    FROM    CAMBRIDGE. 

Seconds. 

To  Buffalo  and  Return -  0.10     1  Repeater. 

"    Chk-ago  "       0.20     3 

"   Om. ha  "       0.33     5 

"  Salt  Lake  "       0.54    9 

"   Virginia  City     "       0.10  11 

"   San  Fraucisco    "       0.7413 

The  actual  time  of  transmission  from  Cambridge  to 
San  Francisco  and  back  was  estimated  not  to  exceed 
three  tenths  of  a  second,  the  "armature  times"  of  the 
thirteen  repeaters  probably  amounting  to  four  or  five 
tenths  of  a  second. 

In  submarine  cables  the  velocity  of  signals  is  con- 
siderably less  than  upon  air  lines.  Prof.  Gould,  in  his 


MODERN    PRACTICE    OF    THE    ELECTRIC    TELEGRAPH.  \^ 

experiments  upon  the  Atlantic  Cable,  found  it  to  ba 
between  7,000  and  8,000  miles  per  second — being 
greater  when  the  circuit  was  composed  of  the  two 
cables,  and  less  when  the  earth  formed  a  part  of  the 
circuit.  His  experiments  seemed  to  show  that,  instead 
of  travelling  around  the  entire  circuit  in  one  direction, 
the  electric  wave,  or  polar  influence,  travelled  both 
ways  from  the  battery,  and  the  signal  was  received 
when  the  two  influences  met.  Experiments  made  on 
air  lines  indicate  that  an  instrument  placed  at  the  cen- 
tral point  of  resistance  between  the  two  poles  of  the 
battery  will  record  the  signal  sooner  than  when  placed 
in  any  other  part  of  the  circuit,  it  being  understood 
that  the  two  terminal  batteries  of  a  telegraph  line  are 
in  effect  but  one,  being  connected  by  the  earth,  which  is 
a  conductor  of  infinitely  small  resistance. 

176.  SPEED  OF  TRANSMISSION. — The  average  rate  of 
transmission,  by  the  most  skilful  operators  upon  the 
Morse  apparatus,  is  about  1,800  words  per  hour.  ;This 
has  been  considerably  exceeded,  however,  by  many 
operators  within  the  past  two  or  three  years.  On  tho 
evening  of  January  28th,  1868,  2,520  words  of  Press 
news  were  sent  from  New  York  to  Philadelphia  in  one 
hour,  and  legibly  copied  by  the  receiving  operator, 
without  a  stop  or  break — the  average  rate  being  forty- 
two,  and  the  maximum  rate  forty-six  words  per  minute. 
On  the  7th  of  February  following  2,630  words  of  Press 
news  were  sent  from  Milwaukee,  Wis.,  to  St.  Paul,  Minn., 
in  one  hour,  the  distance  being  about  400  miles.  On 
the  19th  of  the  same  month  1,352  words  of  Press  news 
were  sent  from  New  York  to  Philadelphia  in  thirty 
minutes,  the  average  rate  being  over  forty-five  words 
per  minute. 

This  is  believed  to  be  the  quickest  time  on  record 
which  has  been  made  in  the  transmission  of  regular 
business  by  the  Morse  system.  The  receiving  opera- 
tor, in  all  the  above  cases,  copied  entirely  from  the 
sound  of  the  instrument. 

The  speed  of  the  printing  instrument  exceeds  that 


146 


APPENDIX  AND  NOTES 


of  the  Morse  under  favorable  circumstances.  On  the 
24th  of  September,  1867,  the  Combination  instrument 
transmitted  from  Albany  to  New  York  1,453  words  of 
Press  news  in  thirty-three  minutes.  It  is  claimed  that, 
on  some  occasions,  as  many  as  2,900  words  per  hour 
have  been  transmitted  by  the  House  instrument. 

177.  COMPARISON  OF  WIRE  GAUGES. — The  different 
sizes  of  wire  employed  for  telegraphic  and  other  pur- 
poses are  designated  by  a  series  of  arbitrary  numbers. 
The  system  known  as  the  Birmingham  gauge  is  the  one 
in  most  general  use  at  the  present  time,  but  is  objec- 
tionable, both  on  account  of  the  irregularity  of  its  gra- 
dations and  the  absence  of  any  authorized  standard — 
wire  of  the  same  number  from  different  makers  often 
varying  considerably  in  its  size.  The  American  gauge 
is  formed  upon  a  geometrical  progression,  and  it  is  to  be 
hoped  will  eventually  supersede  the  old  gauge  :  it  is 
already  employed  to  a  considerable  extent.*  The  fol- 
lowing table  gives  the  diameter,  in  thousandths  of  an 
inch,  of  each  number  in  the  American  and  Birmingham 
gauges : 

TABLE    OF    DIAMETERS    OF    "WIRES. 


Kumber. 

American 
Gauge. 

Birmingham 
Gauge. 

Number. 

American 
Gauge. 

Birmingham 
Gauge. 

0000 

.460 

.454 

19 

.03589 

.042 

000 

1  .40964 

.425 

20 

.OIJI9G 

.035 

00 

.36480 

.380 

21 

.02846 

.032 

0 

.32495 

.340 

22 

.0253"3 

.028 

1 

.28930 

.300 

23 

.02257 

.025 

2 

.25763 

.284 

24 

.0201 

.022 

3 

.22942 

.259 

25 

.0179 

.020 

4 

.20431 

.238 

26 

.01591 

.018 

5 

.iai94 

.220 

27 

.01419 

.016 

I 

.16202 

.203 

28 

.01264 

.014 

1 

.14428 

.180 

29 

.01126 

.013 

8 

.12849 

.165 

30 

.01002 

.012 

9 

.11443 

.148 

31 

.00893 

.010 

10 

.10189 

.134 

32 

.00795 

.009 

11 

.09074 

.120 

33 

.00708 

.008 

12 

.08081 

.109 

34 

.one:; 

.007 

13 

•07196 

.095 

35 

.00561 

.005 

14 

.06408 

.083 

36 

.005 

.004 

15 

.05707 

.072 

37 

.00445 

.... 

16 

.05082 

.065 

38 

.00396 

'..'.'. 

17 

.04526 

.058 

39 

.00353 

.... 

...  18 

.0403 

.049 

40 

.00314 

This  gauge  is  manufactured  by  Darling,  Brown  &  Sharpe,  of  Providence,  E.  I. 


MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH. 


147 


178.'  USEFUL  FORMULAE  FOR  WEIGHT  ANI>  RESISTANCE 
OF  WIRES. — The  following  formulae,  from  Clark's  tables-, 
will  be  found  convenient  in  telegraphic  work : 

The  weight  of  any  iron  wire,  per  statute  mile  of  52SO 
feet,  is  T-IVir  Ibs. ;  c?2  denoting  the  square  of  the  diame: 
ter  of  the  wire  in"  mils  "  or  thousandths  of  an  inch. 

The  conductivity  of  ordinary  galvanized  iron  wirej 
compared  with  pure  copper  100,  averages  about  14,  or 
about  one  seventh  that  of  pure  copper. 

The  resistance  per  statute  mile  of  a  galvanized  iron 
wire  is  about  IMS*",  ohms  at  00°  Fahr. 

The  resistance  of  iron  wire  increases  about  .35  per 
cent,  for  each  degree,  Fahr. 

The  weight  per  statute  mile  of  5280  feet,  of  any  cop 
per  wire,  is  ^/^  Ibs.     A  mile  of  No.  16  wire  weighs 
in  practice  from  63  to  66  Ibs. 

The  resistance  per  statute  mile  of  any  pure  copper 
wire  is  ^^r-2  ohms  at  60°  Fahr.  No.  16  copper  wire 
of  good  quality  has  a  resistance  of  about  19  ohms. 

The  resistance  of  any  pure  copper  wire  I  inches  in 
length,  weighing  n  grains,  —  ^™JL!l  ohms. 

The  resistance  of  copper  increases  as  the  temperar 
hire  rises,  .21  per  cent,  for  each  degree,  Fahr. 

The  conductivity  of  any  copper  wire  is  obtained  by 
multiplying  its  calculated  resistance  by  100,  and  divi- 
ding the  product  by  its  actual  resistance.  Pure  copper 
is  taken  as  100. 

179.  CONDUCTING  POWERS  OF  MATERIALS. — According 
to  the  experiments  of  Mr.  M.  Gr.  Farmer,  made  some 
years  since,  the  relative  electrical  resistance  of  differ- 
ent metals  and  fluids  at  ordinary  temperatures  is  as  fol- 
lows, pure  copper  being  taken  as  100  : 


Silver      ' 

98 

Zinc     '' 

...     370 

Gold        '                 .     .. 

1.13 

IJrass  "  

3.88 

5  63 

11.30 

Lead         ' 

..      ..      10.76 

Nickel                   "     

7.70 

50.00 

2.61 

Palladium  W  ire  

5.50 

Aluminum            "         .... 

1.H 

Platinum      "    . 

.     6.78 

148 


APPENDIX    AND    NOTES. 


: ;  His  experiments  with  fluids  gave  the  following 
results  : 

Pure  Rain  Water 40,653.723,00 

Water,  12  parts ;  Sulphuric  Acid,  1  part 1,305.467.00 

Sulphate  Copper,  1  pound  per  gallon 18,450,00'».0<» 

Saturated  solution  of  common  salt 3,173.000.00 

"              "       of  sulphate  of  zinc 17.330.000,00 

Nitric  Acid,  30  B 1,606,000,00 

>  The  following  table  gives  the  specific  resistance  in 
ohms  of  various  metals  and  alloys,  at  32°  Fahr., 
according  to  the  most  recent  determinations  of  Dr. 
Matthiessen  : 


,  |    vj,:                 NAMS  or  MKTAIA 

Resistance 
of  wire  1 
foot  long, 
weighing 
1  grain. 

Resistance 
of  wire  1 
foot  long, 
1-  1000th 
inch  in 
diameter. 

Approximate 
per  cent, 
variation  in 
resistance 
per  decree 
t-mpt'ratura 
at  20  degrees. 

Silver  annealed      

0  *)014 

9  936 

0377 

"      hard  drawn  

0  ''421 

9  151 

9718 

0  388 

0  2106 

9  940 

0  5849 

12  52 

0  365 

0  5950 

19  74 

0  068<>2 

17  72 

Zinc  pressed  

0  57]  0 

32  22 

0  365 

55  09 

Iron  annealed  

1  2425 

59  10 

1  0785 

75  78 

1  317 

80  36 

0  365 

3  236 

119  39 

0  387 

18  746 

600  00 

0  072 

Platinum  silver  alloy,  hard  or  annealed,  used 
for  standard  resistance  coils  

4  °43 

148  35 

0  031 

German   silver,  hard  or  annealed,  commonly 
used  for  resistance  coils  

2  652 

127  32 

0  044 

Gold  silver  alloy,  2  parts  gold,  1  part  silver, 

2  391 

66  10 

0  og5 

The  use  of  this  table  is  as  follows  :  Suppose  it  is 
required  to  find  the  resistance  at  32°  Fahr.  of  a  con- 
ductor of  pure  hard  copper,  weighing  400  Ibs.  per  knot. 
This  is  equivalent  to  460  grains  per  foot.  The  resist- 
ance of  a  wire  weighing  one  grain  is  found  by  the  table 
to  be  0.2106,  therefore  the  resistance  of  a  foot  of  wire 
weighing  460  grains  will  be  ^J-f5,  but  the  resistance  of 


VODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH.  140 

one  knot  will  be  6087  times  that  of  one  foot,  therefore 
the  resistance  required  will  be  60874Y08'°-!L  =  2.79  ohms. 
If  the  diameter  of  the  wire  be  given  instead  of  its 
weight  per  knot,  the  constant  is  taken  from  the  second 
column.  Thus  the  resistance  at  32°  Fahr.  of  a  knot  of 
pure  hard  drawn  copper  wire  0.1  inch  in  diameter 
would  be  ~~—  =  6.05.  The  resistance  of  wires  is 
materially  altered  by  annealing  them,  and  a  rise  in 
temperature  increases  the  resistance  of  all  metals.  Dr. 
Matthiessen  found  that  for  all  pure  metals  the  increase 
of  resistance  between  32°  and  212°  Fahr.  is  sensibly 
the  same.  The  resistance  of  alloys  is  much  greater 
than  the  mean  of  the  metals  composing  them.  They 
are  very  useful  in  the  construction  of  resistance  coils. 

The  highest  value  which  has  probably  been  found 
for  the  conducting  power  of  pure  copper  is  sixty  times 
that  of  pure  mercury,  according  to  Sabine.  Commer- 
cial copper  may  be  considered  of  good  quality  when 
its  conducting  power  is  over  fifty.  Different  samples 
of  copper  vary  greatly  in  their  specific  conductivity, 
as  may  be  seen  by  the  following  table,  which  gives  the 
result  of  careful  determinations  by  Dr.  Matthiessen, 
the  conducting  power  of  pure  copper  at  59.9°  Fahr. 
being  taken  as  100. 

take  Superior,  native,  not  fused 98.3  at  50  9° 

fused  (commercial) 92.6  at  f,9  0° 

Burr.iBurrn 88.7  at  67.2' 

Best  sck-eted 81.3  at  57.5° 

Biigl.t  copper  wire 72.2  at  «".2° 

Tough  copper 71.0  at  G3  1° 

Dem -doff 59.3  at  54.8° 

Kio  Tiiito 1  i.2  at  58.6° 

Thus  Rio  Tinto  copper  possesses  no  better  conduct-, 
ing  power  than  iron.  This  shows  the  great  importance 
of  testing  the  conductivity  of  the  wire  used  in  the 
manufacture  of  electro-magnets,  cables,  etc. 

180.  INTERNAL  RESISTANCE  OF  BATTERIES. — This  may 
be  measured  by  the  sine  or  tangent  galvanometer. 
Place  the  battery  to  be  measured  in  circuit  with  a  sine 
galvanometer  giving  a  certain  deflection.  Insert  resist- 
ance till  the  sine  of  the  deflection  becomes  half  what 


150 


APPENDIX    AND    NOTES. 


it  originally  was.  The  total  resistance  of  the  circuit 
is  now  doubled,  and  the  resistance  added  is,  therefore, 
equal  to  the  original  resistance.  Deduct  the  resistance 
of  the  galvanometer  and  connections  from  the  resist- 
ance added,  and  the  remainder  is  the  resistance  of  the 
battery. 

"  Second  Method* — Let  D  =  the  deflection  obtained 
with  the  battery  in  circuit  with  a  galvanometer  whose 
deflections  arc  proportional,  and  some  resistance  r; 
and  d  the  deflection  with  some  larger  resistance  li  (the 
resistance  of  the  galvanometer  being  included  in  II  and 
r\  and  let  x  =  the  resistance  of  the  battery. 

Then  D:  d  ::  P.  -i- x  :  r  +  x 

and  *  =        11-  r>  ~  P  *_L> 

ii  D  —  d 

-  In  using  this  method  any  other  resistance  y  may  be 
included  with  x,  and  the  formula  becomes — 

'.',    (d  y  R)-  (D  x  r)  , 

D  —  d, 

and  by  deducting  x  we  get  the  value  of  y,  or  if  y  be 
large  in  comparison  with  x,  the  latter  may  be  neglected. 
By  this  method  one  resistance  r  may  be  compared  with 
another. 

The  approximate  resistance  of  the  batteries  in  com- 
mon use  is  as  follows,  according  to  Mr.  Farmer  : 

ftrove 0.41  ohms 

„-   ''~    Carbon O.C  t      " 

Daniell 1.70      " 

181.  ELECTRO-MOTIVE  FORCE  OF  DIFFERENT  BAT-" 
TERIES. — The  following  table  gives  approximately  the 
electro  motive  force  of  various  batteries,  being  the 
mean  of  numerous  observations  taken  on  a  sine  galvan- 
ometer by  Mr.  Latimcr  Clark. f  The  electro-motive 
force  of  batteries  is  within  certain  limits  very  variable, 
depending  on  a  variety  of  undetermined  causes.  It  {3 
not  much  affected  by  temperature. 


Clark,  Eedrical  Measurement,  p.  100.          \  Electrical  Measurement,  p.  108. 


MODERN    VUACTICE    OF   THE    ELECTRIC    TELEGRAPH.  151 

Grove's. 100 

Carbo-.  with  bi-chromate  solution 107 

Daniell's 5G 

Smee's  (when  not  ia  action) 57 

"      (when  iu  action)  about 25 

Copper  and  zinc  in  acid  (Wollaston) 46 

Sulphate  mercury  and  graphite  (Marie  Davy) 76 

Chloride  silver 62 

Chloride  lead 30 

When  connected  on  short  circuit,  the  electro-motive 
force  of  several  of  the  batteries,  especially  Smee's  and 
Wollaston 's,  will  fall  off  50  per  cent,  or  more,  owing  to 
the  formation  of  hydrogen  on  the  negative  plate. 
Grove's  and  Daniell's  do  not  so  fall  off,  because  tho 
hydrogen  is  reduced  by  the  nitric  acid  in  one  case  and 
by  the  oxygen  in  the  other. 

182.  MEASUREMENT  OF   ELECTRO-MOTIVE  FORCE.* — 
When  a  number  of  cells  are  joined  up  in  circuit  with, 
.but  in  opposition  to,  a  number  of  other  cells  with  a 
galvanometer  inserted,  by    adjusting   the   number  of 
cells  so  that  no  current  passes,  the  relative  electro- 
motive force  of  the  two  batteries  may  be  determined.  ' 

Second  Method.— Call  the  electro-motive  forces  of  the 
two  batteries  E  and  E';  join  them  up  successively  in 
circuit  with  the  same  galvanometer,  and  by  varying 
the  resistance,  cause  them  both  to  give  the  same  de- 
flection ;  their  forces  will  then  be  in  direct  proportion 
to  the  total  resistances  in  circuit  in  each  case,  or 

«•  -  I  X  £ 

where  E  represents  the  resistance  with  E  (including 
that  of  battery,  galvanometer,  and  the  adjustable  re- 
sistance) and  R'  with  E'. 

183.  FORCES  OF  ELECTRO-MAGNETS.— The  laws  which 
govern  the  forces  of  electro-magnets  have  been  investi- 
gated by  Lenz,  Jacobi  and  Miiller. 

Let  M  •=  the  magnetic  force  of  the  electro-magnet 

n   —  the  number  of  convolutions  of  wire. 

d   =  the  diameter  of  the  soft  iron  core. 

Q  =  tho  quantity  of  electricity  in  circulation, 
and  c  a  constant  multiplier. 

Then     M  =  c  n  Q  V  d. 

*  Clark,  Electrical  Measurement,  p.  103. 


152       :"'Vs*  APPENDIX   AND  NOTES. 

This  law  only  holds  good  for  bars  of  iron  whose 
length  is  considerably  greater  than  their  diameter,  for 
feeble  currents  of  electricity,  and  under  the  supposi- 
tion that  the  number  of  convolutions  of  wire  is  not  so 
great  as  materially  to  diminish  the  influence  exerted 
by  the  outer  coils  upon  the  bar  of  iron.  These  condi- 
tions are  fulfilled  in  the  electro-magnets  used  for  tele- 
graphic purposes. 

It  will  be  noticed,  in  the  above  formulae,  that  M  in- 
creases directly  as  Q  and  as  n,  but  Q  decreases  as  n 
increases,  supposing  the  electric  force  to  remain  con- 
stant. Hence  it  is  evident  that  a  certain  proportion 
between  the  resistance  of  the  wire  and  that  of  the 
remaining  portions  of  the  circuit  must  be  preserved  to 
obtain  the  maximum  magnetic  force.  This  relation  is 
found  to  be  the  following: 

When  the  resistance  of  the  coils  of  the  electro-magnet 
is  equal  to  the  resistance  of  the  rest  of  the  circuit,  i.  e.,  the 
conducting  wire  and  battery,  the  magnetic  force  is  a  maxi- 
mum* 

The  application  of  this  law  to  a  telegraphic  circuit 
would  be  to  make  the  sum  of  the  resistances  of  all 
the  magnet  coils  in  circuit  equal  to  the  resistance  of 
the  line  and  batteries,  but  as  in  practice  the  resistance 
of  a  telegraphic  circuit  varies,  being  considerably  re- 
duced by  defective  insulation,  the  total  resistance  of 
the  instruments  should  be  less  than  that  of  the  line 
when  in  good  condition,  to  attain  the  best  results  dur- 
ing unfavorable  weather. 

ELECTRICAL   FORMULAE. 

184.  OHM'S  LAW. — Let  C  =  the  quantity,  or  strength, 
or  force,  or  intensity  of  the  current,  as  it  is  variously 
called. 

Let  n  =  the  number  of  cells. 
"    E  -  the  electro-motive  force  in  each  cell. 
"   R  =  the  internal  resistance  of  each  cell. 
"   r  =  the  resistaucea  exterior  to  tho  battery. 
Then        c  =        n  E 

»  tt  +  r. 

*  Noad'a  Students'  Text-book  of  Electricity,  p.  277. 


MODERN  PRACTICE  OF  THE  ELECTRIC  TELEGRAPH.  153 

185.  PARALLEL  OR  DERIVED  CIRCUITS.  —  1.  The  joint 
resistance  of  any  two  parallel  or  derived  circuits,  whose 
resistances  =  a  and  b,  is  equal  to  their  product  divided 
by  their  sum,  or 


0  +  6 


2.  The  joint  resistance  of  any  three  circuits,  a,  b 
and  c,  is 

a  5  c 


R  = 


3.  The  joint  resistance  of  any  number  of  circuits  is 
obtained  by  adding  their  reciprocals  together,  thus : 


"=--;-- 

b 


186.  GALVANOMETERS    AND   SHUNTS. — 1.  The  joint 
resistance  of  a  galvanometer  and  shunt  is  as  follows: 

Let  g  =  resistance  of  galvanometer. 
s  =  resistance  of  shunt. 

ThenR=     JLL. 

g  +  s 

2.  The  multiplying  power  of  any  shunt  is  equal  to 

a  s 

3.  To  prepare  a  shunt  having  some  definite  multiply- 
ing power,  for  example  10  100  or  1,000, 

Let  n  =  the  multiplying  power  required, 
Then  s  =    — -— 

187.  FORMULA  FOR  THE  LOOP  TEST  (127  . — Let  x  = 
resistance  of  shortest  part  of  the  loop. 

y   =  resistance  of  longest  part 

L   =  total  resistance  of  both. 

R  —  resistance  added  to  shortest  part,  to  make  it  equal  to  the  longer. 

Then          x  +  y  =  L. 
y  =.  x  +  R. 

and        X  =  L  ~  R 


154  APPENDIX   AND   NOTES. 

188.  BLAVIER'S  FORMULA  FOR  LOCATING  A  FAULT 
(128).  —  Let  R  =  resistance  of  line  when  in  good 
order,  S  =  resistance  of  defective  line  when  distant 
end  is  to  ground,  and  T  the  resistance  when  it  is  dis- 
connected or  open  at  distant  end. 

The  distance  (x)  of  the  fault  from  the  testing  station 
will  be 

x  =.  S  —  ^  -4-  T  li  —  T  8  —  It  S~ 
or  x  =.  S  —  ^(tt  —  .S)  x  (I1  —  S)i 

and  the  resistance  of  the  fault  (z)  will  be 


z  =_  T  —  S  +  ^&~+  T  It  ~"T~S~ 
or  z  =  T  —  S  +  "'(IT—  S)  *  (T  —  b) 


189.  MEASURES  OF  RESISTANCE.  —  1.0456  Siemen's 
units  =  1  ohm.  To  convert  Siemen's  units  into  ohms. 
multiply  by  .9564. 

1  Varley'a  unit  =  25  ohms. 
1  Megohm  =  1,000,0,0  ohms. 
-1  Microhm  =  1<inrjiinnr  ohms. 

STRAIN  OF  SUSPENDED  WIRES.*  —  The  ordinary  dip 
of  line  wires,  for  a  span  of  80  yards,  is  about  18  inches 
in  mild  weather  ;  this  gives  with  No.  8  wire  a  strain 
of  420  Ibs.,  its  breaking  weight  being  about  1,300  Ibs.  — 
(Culley.) 

.-  The  strain  varies  directly  as  the  weight  of  the  wire, 
arid  inversely  as  the  dip  or  versine  ;  it  increases  as 
the  square  of  the  span  if  the  dip  be  constant  ;  but  to 
preserve  a  given  strain  the  dip  or  versine  must  in- 
crease as  the  square  of  the  span,  or, 

^  \     .  -      .  L!  :  P  :  :  V  j  v.  f 

The  strain  is  greater  at  the  point  of  suspension  than-' 
at  the  lowest  point  of  the  span,  by  a  quantity  (equal 
to  the  weight  of  a  length  of  wire  of  the  same  height  as 
the  versine)  which  maybe  neglected  in  practice.  Call-' 
ing  /  the  length  of  the  span  in  feet,  w  the  weight  in 

*  Clark.  Heaiatance  Measurement,  p.  154. 


MODERH    PRACTICE    OF    THE   ELECTRIC    TELEGRAPH.  155 

cwts.  of  one  statute  mile,  v  the  versine  in  inches,  and 
s  the  strain  in  Ibs., 

P  X  w 

Strain  =  31  43  x  y  Ibs.  approximately. 

P  X  w 
and  dip  ^—-         inches. 


When  both  supports  are  of  the  same  height  the 
lowest  point  in  the  curve  will  be  in  the  centre  of 
the  span  ;  but  if  one  support  be  higher  than  the 
other  the  lowest  point  will  be  near  the  lower  support, 
so  that  the  greater  portion  of  the  weight  is  borne  by 
the  higher  pole.  In  calculating  the  strain  the  wire 
should  be  considered  as  if  prolonged  beyond  the  lower 
end  to  a  point  equal  in  height  to  the  upper  one,  and 
the  strain  will  be  proportional  to  the  length  thus  in- 
creased, or  to  twice  the  distance  from  the  top  to  the 
bottom  of  the  dip. 

The  weight  of  a  wire  increases  with  its  strength,  the 
quality  being  the  same.  The  advantage  of  using  thin 
wire  for  long  spans  is  only  in  diminishing  the  weight 
upon  the  supports. 

Iron  expands  TTTTIT  of  its  length,  or  about  4T'o-  inches 
per  mile  for  every  ten  degrees  of  heat.  —  (Culley.) 


THE   KNO. 


I  N  D  E  X 


ALPHABET — Morse,  101 ;  Formation  of  the,  96  ;  Exercises  for  practising,  97; 

Spaced  letters  in,  101. 

AMERICAN  COMPOUND  WIKE,  the,  89-104. 

APPARATUS,  adjustment  of  the,  36. 

APPENDIX  AND  NOTES,  116. 

ARMATURE,  22. 

ATLANTIC  CABLES,  method  of  working,  141. 

BATTERIES  -Insulation  of,  20  ;  P.irafflned  jars  for,  20;  Arrangement  of,  26; 
Reversed,  57  ;  Table  of  Resistances  of,  117 ;  Table  of  electro-motive 
forces  of,  117;  Measurement  of  electro-motive  forces  of,  151;  Working 
several  lines  from,  71;  Electrical  tension  of,  124. 

BATTERY,  CARBON,  OR  ELECTROPOION,  17;  Setting  up  the,  18;  Solution,  recipe' 
for  making,  19  ;  Renewal  of  the,  19  ;  Resistance  of,  117,  151  ;  Electro- 
motive force  of,  117,  151. 

BATTEISY,  DANIELL  -12;  Effect  of  continued  action  on  the,  13;  Deposit  of  cop- 
per upon  porous  cup  of  the,  14  ;  Renewal  of  the,  14  ;  Application  to 
main  circuit  of  the,  15. 

BATTERY,  GROVE — 15;  Setting  up  a,  16  ;  Renewal  of  the,  17;  Resistance  of, 
117,  150;  Electro-motive  force  of,  117,  151. 

BATTERY,  GRAVITY— 106;  Callaud,  106;  Hill,  106;  Manner  of  setting  up,  107; 
Maintenance  of,  107  ;  Internal  resistance  of,  117,  149  ;  Eloctro-motiva 
force  of,  117. 

BATTERY  POWER — Distribution  of,  70. 

BINDING  SCREWS,  57. 

BRIDGE,  Wheatstoue's,  109,  110. 

BUTTON  REPEATER— Wood's,  46,  Edison's,  134. 


CABLES,  93;  Making  joints  in,  94. 

CABLES,  Atlantic—  Mo 3e  of  working  the,  141. 

CIRCUIT,  57;  Simple  galvanic,  9;  Earth,  26;  Metallic,  57;  Local,  30,  57. 

CIRCUITS,  Telegraphic,  24,  25. 

CIRCUIT  CHANGER,  for  locals,  56. 

COMPOUND  WIRE,  the  American,  89, 104. 

COMBINATION  PRINTING  INSTRUMENT,  the,  27. 

COMBINATION,  locals,  55. 

CONDENSER,  used  in  working  Atlantic  Cable,  141. 

CONDUCTIVITY  RESISTANCE,  testing  for,  87. 

CONDUCTORS  AND  NON-CONDUCTOBS,  5 ;  Table  of,  5. 


158  INDEX. 

CONDUCTING  POWEB  OF  MATERIALS,  Table  of,  147. 

CONSTRUCTION,  telegraphic,  notes  on,  89. 

CBOSS,  57,  73  ;  Weather  do.,  57,  73  ;  Testing  for,  76  ;  To  find  the  distance  of, 

85. 

CBOSS  CONVICTING  WIBES,  57,  75. 
CUKEENT,  Eflfective  force  of,  24;  Laws  of,  64. 
CURRENTS,  Earth,  88,  141. 

DEBITED  Ciscurrs,  formula  for,  153. 

DISCONNECTION,  73;  Testing  for,  75;  Partial  do.,  73;  Testing  for  75. 

DIAMETERS  OF  WIBES,  table  of,  146. 

DOUBLE  TRANSMISSION,  131. 

EARTH  CIRCUIT,  the,  26 ;  Resistance  of,  26. 

EARTH  CURRENTS,  88,  141. 

ELECTRIC  CURRENTS,  laws  of  the,  64. 

ELECTRIC  SIGNALS,  velocity  of,  144. 

ELECTRO-MAGNETS,  forces  of,  151. 

ELECTRO-MAGNET,  21,  22;  Cores  of,  21;  Construction  of,  22. 

ELECTRO-MAGNETISM.  21. 

ELECTRO-MOTIVE  FORCES,  measurement  of,  151;  Table  of,  117,  151. 

ESCAPE,  57,  63,  73  ;  Testing  for,  75  ;  Blavier's  formula  for  locating,  84,  154; 

Effects  of  upon  the  circuit,  63. 
EQUIPMENT  OF  TELEGRAPH  LINES,  the,  117. 

FAULTS,  Testing  for  distance  of,  80. 

FORMULA — Blavier's,  for  locating  an  escape,  84,  154  ;  For  weight  and  resist- 
ance of  wires,  147  ;  Electrical,  152;  Ohm's,  152  ;  Parallel  or  derived  cir- 
cuits, 153;  Joint  resistance  of  parallel  circuits,  153;  Galvanometers  and 
shunts,  153;  For  the  loop  test,  153. 

GALVANOMETER,  21  ;  Testing  with,  78  ;  Differential,  78, 109  ;  Siemens  Univer- 
sal, 108,  111;  Bradley 's  tangent,  135;  Thompson's  reflecting,  137. 
GALVANOMETERS  AND  SHUNTS,  formula  for  resistance  of,  153. 
GAUGES,  wire,  comparison  of,  146. 
GROUNDS,  testing  for,  76. 

GROUND  CONNECTIONS,  93;  Defective,  testing  for,  74. 
GROUND  SWITCH,  36,  38. 

INSULATION,  58  ;  English  standard  of,  86;  Mileage,  86. 

INSULATOR— Glass,  59  ;  Wade,   60  ;   Hard  rubber,  60  ;  Lefferte',  61  ;  Brooks'. 

61,  62. 

INSULATOBS,  mode  of  testing,  62;  Fixing  upon  poles,  91. 
INTEBRUPTIONS  UPON  LINES,  73. 
INTERNAL  RESISTANCE  OF  BATTERIES,  149. 

JOINTS  OB  SPLICES,  90;  In  Cables,  method  of  making,  94. 
JOINT  RESISTANCE,  67,  121;  Formula  for,  126. 


INDEX.  159 

LIGHTNING  ARRESTERS,  42;  Chester's  plate,  43;  Bradley's,  43. 

LOCALS,  57;  Combination,  55. 

LOCAL  CIRCUIT  CHANGEK,  56. 

LINE,  57. 

LOOP,  57. 

LOOP  TEST,  the,  81;  Formula  for,  ib3. 

LEADING  WIRES  INTO  OFFICES,  92. 

LEARNERS.  Hiuts  to,  97. 

MAGNETS,  Electro,  20;  Formula  for  forces  of,  151. 

MEASURES,  Electrical,  154. 

MEASUREMENT,  Electrical,  25;  Standards  of,  25, 154;  Advantages  of  testing  by, 

.80. 
MORSE  SYSTEM,  the,  26,  28;  Signal  key  of  the,  28;  Register  of  the,  29;  Relay 

magnet  ol  the,  30;  Alphabet  of  the,  101. 
NOTES  ON  TELEGRAPHIC  CONSTRUCTION,  89. 
NOTES,  APPENDIX  AND,  116. 

OHM,  definition  of  the,  25. 

OHM'S  LAW,  04,  152;  Practical  application  of,  64. 

OFFICES,  leading  wires  into,  92;  Fitting  up,  92;  Arrangement  of  wires  in,  34, 
35. 

POLES,  Telegraph,  89. 

PRINTING  TELEGRAPH — the  combination,  27;  Pope  and  Edison's,  112. 

QUANTITY,  Electrical,  11. 

RESISTANCE,  10;  Of  the  circuit,  42  ;  Units  of,  25,  154  ;  Conductivity,  testing 
for,  87  ;  Of  unsoldered  joints,  87  ;  of  relays,  117;  Of  Batteries,  table  of 
117;  Of  different  metals,  table  of,  148;  Of  liquids,  148;  Of  copper,  149; 
Of  batteries,  to  ascertain  the,  149. 

RESISTANCE  COILS,  25;  Testing  with,  78. 

REGISTER,  Morse,  the,  29;  Mainline,  the,  34;  Proper  resistance  of,  118. 

RELAY,  the  Morse,  30;  Pocket,  the,  32. 

RELAYS — Proper  resistance  for,  117. 

READING  BY  SOUND,  102. 

REPEATERS,  45  ;  Wood's  button,  46  ;  Hicks'  automatic,  47  ;  Milliken'g,  50  ; 
Bnnnell's,  52;  Edison's  button,  107. 

RECENT  IMPROVEMENTS  IN  TELEGRAPH  PRACTICE,  104. 

SERVICE,  TELEGRAPHIC — Technical  terms  used  in  the,  57. 

SIEMENS' UNIT,  154;  Universal  galvanometer,  108,  111. 

SHUNTS— of  galvanometer,  80 ;  Formula  for  resistance  of,  153 ;  Multiplying 

power  of,  80,  153. 
SIGNAL  KEY,  the  Morse,  28. 
SIGNALS  ELECTRIC,  velocity  of,  144 . 
SOUNDER,  the  Morse,  32;  Main  line,  the,  33;  Proper  resistance  of,  118. 


16Q  INDEX. 

SOUND,  reading  by,  102.  * 

SPLICES  OK  JOISTS,  90. 

SPEED  OF  TRANSMISSION,  145. 

STATIONS,  intermediate,  26  ;  Arrangement  of,  35  ;  Terminal,  arrangement  of, 

34. 

STBAIN  OF  SUSPENDED  WIKES,  151. 
SWITCH— Ground,  36,  38  ;  Button,  37;  Plug,  39  ;  Universal,  40  ;  Culgan,  40  ; 

Jones'  lock,  41. 
SWITCHES  OB  COMMCTATOBS,  37. 

TECHNICAL  TERMS  USED  IN  THE  TELEGRAPH  SERVICE,  57. 

TENSION,  electrical,  11;  Of  batteries  and  lines,  124;  Diagram  of,  128. 

TELEGRAPH  LINES— Equipment  of,  116  ;  Electrical  tension  of,  124  ;  Working 
capacity  of,  121. 

TELEGRAPHIC  CONSTRUCTION,  notes  on,  89. 

TEST,  the  loop,  81 . 

TESTING — Insulators,  62;  Telegraph  lines,  73  ;  For  disconnection,  74;  Partiaf 
disconnection,  75  ;  Escape,  75  ;  Cross,  76  ;  Ground,  76  ;  By  galvano- 
meter and  resistance  coils,  78  ;  For  distance  of  faults,  80  ;  By  measure- 
ment, advantages  of,  86;  For  conductivity  resistance,  87. 

TRANSMISSION— Double,  131  ;  Speed  of,  145. 

UNITS  OF  ELECTRICAL  MEASUREMENT — British  Association  or  Ohm,  25,  154  ; 
Siemens',  154;  Varley's,  154. 

VELOCITY  OF  ELECTRIC  SIGNALS,  144. 
VARLEY'S  UNIT  OF  MEASUREMENT,  154. 

WEATHER  CROSS,  57. 

WIRES — To  cross  connect,  57,  75  ;  To  put  straight,   57  ;  To  ground,  57  ;  To 

open,  57  ;  Arrangement  of,  upon  the  poles,  90  ;  Method  of  splicing,  90  ; 

Strain  of,  when  suspended,  154. 
WIRE— For  telegraph  lines,  89  ;  American  compound,  89,  104  ;  Galvanized, 

90  ;  Table  of  diameters  of,  119;  Iron,  formula  for  ascertaining  weight 

of,  147  ;  Kesistance  of,  147  ;  Copper,  weight  of,   147 ;  Resistance  of, 

147. 

WIRE  GAUGES,  comparison  of,  146. 
WHEATSTONE'S  BRIDGE,  109,  110. 
WORKING  CAPACITY  OF  TELEGRAPH  LINES,  121  ;  How  to  increase,  121. 


SCIENTIFIC   BOOKS. 


'  (J.  B.)  Hydraulic  Experiments.  Lowell  Hydraulic  Ex- 
-»-  periments — being  a  Selection  from  Experiments  on  Hydraulic 
Motors,  on  the  Flow  of  Water  over  Weirs,  and  in  Open  Canals  of 
Uniform  Rectangular  Section,  made  at  Lowell,  Mass.  By  J.  B. 
.FRANCIS,  Civil  Engineer.  Second  edition,  revised  and  enlarged,  in- 
cluding many  New  Experiments  on  Gauging  Water  in  Open^Canals, 
and  on  the  Flow  through  Submerged  Orifices  and  Diverging  Tubes. 
With  23  copperplates,  beautifully  engraved,  and  about  100  new 
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Most  of  the  practical  rules  given  in  the  books  on  hydraulics  have  been  determined  from  ex- 
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In  applying  them  to  the  large  operations  arising  in  practice  in  this  country,  the  engineer  cannot 
but  doubt  their  reliable  applicability.  The  parties  controlling  the  great  water-power  furnished 
by  the  Merrimack  River  at  Lowell,  Massachusetts,  felt  this  so  keenly,  that,  they  have  deemed  it 
necessary,  at  great  expense,  to  determine  anew  some  of  the  most  important  rules  for  gauging 
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several  series  of  experiments  on  a  large  scale,  a  selection  from  which  are  minutely  detailed  in 
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Essex  Company  across  the  Merrimack  River  at  Lawrence,  Massachusetts  ;  twenty-one  experi- 
ments on  the  effect  of  observing  the  depths  of  water  on  a  weir  at  different  distances  from  the 
weir ;  an  extensive  series  of  experiments  made  for  the  purpose  of  determining  rules  for  gang- 
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In  1855  the  proprietors  of  the  Locks  and  Canals  on  Merrimack  River,  at  whose  expense  mo«t 
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through  a  submerged  Venturi's  tube,  in  which  a  larger  flow  was  obtained  than  any  we  find  re- 
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FRANCIS  (J.   B.)  On  the  Strength  of  Cast-iron  Pillars,  with  Tables 
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FRANCIS,  Civil  Engineer,     i  vol.,  8vo.    Cloth.     $2. 


Scientific  Books.  25 

WILLIAMSON  (R.  S.)  On  the  Use  of  the  Barometer  on  Surveys 
and  Reconnaissances.  Part  I.  Meteorology  in  its  Connection 
with  Hypsometry.  Part  II.  Barometric  Hypsometry.  By  R.  S. 
WILLIAMSON,  Bvt.  Lieut.  -Col.  U.  S.  A.,  Major  Corps  of  Engineers. 
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"  SAN  FRANCISCO,  CAL.,  Feb.  27,  1867. 
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"R.  S.  WILLIAMSON, 
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TUNNER  (P.)     A  Treatise  on  Roll-Turning  for  the  Manufacture  of 
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SHAFFNER  (T.  P.)  Telegraph  Manual.  A  Complete  History  and 
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$6.50. 

IN^FIE  (WM.)  Mechanical  Drawing.  A  Text-Book  of  Geomet- 
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MINIFIE  (WM.)   Geometrical  Drawing.     Abridged  from  the  octavo 
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M 


26  D.  Van  Nostrand's  Publications. 

PEIRCE'S  SYSTEM  OF  ANALYTIC  MECHANICS.  Physical 
and  Celestial  Mechanics,  by  BENJAMIN  PEIRCE,  Perkins  Professor 
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4to.  Cloth.  $10. 

/""*  ILLMORE.     Practical  Treatise  on  Limes,  Hydraulic  Cements,  and 
V-J     Mortars.     Papers  on  Practical  Engineering,  U.  S.  Engineer  De- 

partment, No.  9,  containing  Reports  of  numerous  experiments  con- 

ducted in  New  York  City,  during  the  years  1858  to  1861,  inclusive. 

By  Q.  A.  GILLMORE,  Brig.  -General  U.  S.  Volunteers,  and  Major  U. 

S.  Corps  of  Engineers.     With  numerous  illustrations.     One  volume, 

octavo.     Cloth.     $4. 

ROGERS  (H.   D.)     Geology  of  Pennsylvania.     A  complete  Scien- 
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Geologist.     3  vols.,  4to.,  plates  and  maps.     Boards.     $30.00. 

BURGH  (N.  P.)  Modern  Marine  Engineering,  applied  to  Paddle 
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the  whole  being  an  exposition  of  the  present  practice  of  the  follow- 
ing firms  :'  Messrs.  J.  Penn  &  Sons;  Messrs.  Maudslay,  Sons,  & 
Field  ;  Messrs.  James  Watt  &  Co.  ;  Messrs.  J.  &  G.  Rennie  ;  Messrs. 
R.  Napier  &  Sons  ;  Messrs.  J.  &  W.  Dudgeon  ;  Messrs.  Ravenhill 
&  Hodgson  ;  Messrs.  Humphreys  &  Tenant  ;  Mr.  J.  T.  Spencer, 
and  Messrs,  Forrester  &  Co.  By  N.  P.  BURGH,  Engineer.  In  one 
thick  vol.,  4to.  Cloth.  $30.00.  Half  morocco.  $35.00. 

ING.     Lessons  and  Practical  Notes  on  Steam,  the  Steam-Engine, 
Propellers,   &c.  ,   &c.,   for  Young  Marine  Engineers,   Students, 
and  others.     By  the  late  W.   R.   KING,  U.  S.  N.     Revised  by  Chief- 
Engineer  J.  W.  KING,  U.  S.  Navy.     Ninth  edition,  enlarged.     8vo. 
Cloth.     $2. 

ARD.     Steam  for  the  Million.     A  Popular  Treatise  on  Steam  and 
its  Application  to  the  Useful  Arts,  especially  to  Navigation.     By 
J.  H.  WARD,  Commander  U.   S.   Navy.     New  and  revised  edition. 
i  vol.,  8vo.     Cloth.     $i. 

ALKER.     Screw  Propulsion.      Notes  on  Screw  Propulsion,   its 
Rise  and  History.     By  Capt.  W.   H.  WALKER,  U.  S.  Navy,      i 
vol.,  8vo.     Cloth.     75  cents. 

THE  STEAM-ENGINE  INDICATOR,  and  the  Improved  Mano- 
meter Steam  and  Vacuum  Gauges  :  Their  Utility  and  Application. 
By  PAUL  STILLMAN.     New  edition,      i  vol.,  I2mo.     Flexible  cloth. 
$i. 

T  SHERWOOD.     Engineering  Precedents  for  Steam  Machinery.     Ar- 
1-     ranged  in  the  most  practical  and  useful  manner  for  Engineers.     By 
B.   F.   ISHERWOOD,  Civil  Engineer  U.  S.  Navy.     With  illustration* 
Two  volumes  in  one.     8vo.     Cloth.     $2.50. 


K 


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Scientific  Books.  27 

POOR'S  METHOD  OF  COMPARING  THE  LINES  AND 
DRAUGHTING  VESSELS  PROPELLED  BY  SAIL  OR 
STEAM,  including  a  Chapter  on  Laying  off  on  the  Mould-Loft 
Floor.  By  SAMUEL  M.  POOK,  Naval  Constructor.  i  vol.,  8vo. 
With  illustrations.  Cloth.  $5. 

SWEET  (S.  H. )  Special  Report  on  Coal ;  showing  its  Distribution, 
Classification  and  Cost  delivered  over  different  routes  to  various 
points  in  the  State  of  New  York,  and  the  principal  cities  on  the 
Atlantic  Coast.  By  S.  H.  SWEET.  With  maps,  i  vol.,  8vo.  Cloth. 
$3- 

A  LEXANDER  (J.   H.)     Universal  Dictionary  of  Weights  and  Meas- 
•t*-     ures,  Ancient  and  Modern,  reduced  to  the  standards  of  the  United 
States  of  America.     By  J.    H.  ALEXANDER.     New  edition,      i  vol., 
8vo.     Cloth.     $3.50. 

"  As  a  standard  work  of  reference  this  book  should  be  in  every  library ;  it  is  ote  which  wo 
have  long  wanted,  and  it  will  save  us  much  trouble  and  research."— Scientific  American. 

CRAIG  (B.  F. )     Weights  and  Measures.     An  Account  of  the  Deci- 
mal System,  with  Tables  of  Conversion  for  Commercial  and  Scien- 
tific Uses.     By  B.  F.  CRAIG,   M.  D.     i  vol.,  square  '321110.     Limp 
cloth.     50  cents. 

"  The  most  lucid,  accurate,  and  useful  of  all  the  hand-books  on  this  subject  that  we  have  yet 
Been.  It  gives  forty-seven  tables  of  comparison  between  the  English  and  French  denominations 
of  length,  area,  capacity,  weight,  and  the  centigrade  and  Fahrenheit  thermometers,  with  clear 
instructions  how  to  use  them :  and  to  this  practical  portion,  which  helps  to  make  the  transition 
as  easy  as  possible,  is  prefixed  a  scientific  explanation  of  the  errors  in  the  metric  system,  and 
how  they  may  be  corrected  in  the  laboratory." — Nation. 

BAUERMAN.  Treatise  on  the  Metallurgy  of  Iron,  containing 
outlines  of  the  History  of  Iron  manufacture,  methods  of  Assay, 
and  analysis  of  Iron  Ores,  processes  of  manufacture  of  Iron  and 
Steel,  etc.,  etc.  By  H.  BAUERMAN.  First  American  edition.  Re- 
vised and  enlarged,  with  an  appendix  on  the  Martin  Process  for 
making  Steel,  from  the  report  of  Abram  S.  Hewitt.  Illustrated 
with  numerous  wood  engravings.  I2mo.  Cloth.  $2.50. 

"  This  is  an  important  addition  to  the  stock  of  technical  works  published  in  this  country.  It 
embodies  the  latest  facts,  discoveries,  and  processes  connected  with  the  manufacture  of  iron 
and  steel,  and  should  be  in  the  hands  of  every  person  interested  in  the  subject,  as  well  as  in  all 
technical  and  scientific  libraries."— Scientific  American. 

HARRISON.     Mechanic's  Tool  Book,  with  practical -rules  and  sug- 
gestions,  for- the  use  of  Machinists,  Iron  Workers,  and  others. 
By  W.   B.    HARRISON,   associate  editor  of  the  "American  Artisan." 
Illustrated  with  44  engravings.      I2mo.      Cloth.      $2.50. 

"  This  work  is  specially  adapted  to  meet  the  wants  of  Machinists  and  workers  in  iron  gener- 
ally. It  is  made  up  of  the  work-day  experience  of  an  intellrgent  and  ingenious  mechanic,  who 
had  the  faculty  of  adapting  tools  to  various  purposes.  The  practicability  of  his  pUns  8t>4  sug- 
gestions ire  made  apparent  even  to  the  unpractised  eye  by  a  series  of  well-executed  v,'on&  ro 
p*;-\n«s."— Philadelphia  Inquirer. 


N 


28  D.  Van  Nostrands  Publications. 

"DLYMPTON.  The  Blow-Pipe  :  A  System  of  Instruction  in  its  prao 
-L  tical  use,  being  a  graduated  course  of  Analysis  for  the  use  of 
students,  and  all  those  engaged  in  the  Examination  of  Metallic 
Combinations.  Second  edition,  with  an  appendix  and  a  copious 
index.  By  GEORGE  W.  PLYMPTON,  of  the  Polytechnic  Institute, 
Brooklyn.  I2mo.  Cloth.  $2. 

"  This  manual  probably  has  no  superior  in  the  English  language  as  a  text-book  for  beginners, 
or  as  a  guide  to  the  student  working  without  a  teacher.  To  the  latter  many  illustrations  of  the 
utensils  and  apparatus  required  in  using  the  blow-pipe,  as  well  as  the  fully  illustrated  descrip- 
tion of  the  blow-pipe  flame,  will  be  especially  serviceable."— New  York  Teacher. 

UGENT.  Treatise  on  Optics  :  or,  Light  and  Sight,  theoretically 
and  practically  treated  ;  with  the  application  to  Fine  Art  and  In- 
dustrial Pursuits.  By  E.  NUGENT.  With  one  hundred  and  three 
illustrations.  I2mo.  Cloth.  $2. 

"  This  book  is  of  a  practical  rather  than  a  theoretical  kind,  and  is  designed  to  afford  accurate 
and  complete  information  to  all  interested  in  applications  of  the  science."— Bound  Table. 

O  ILVERSMITH  (Julius).     A  Practical  Hand-Book  for  Miners,  Met- 
^-?     allurgists,  and  Assayers,  comprising  the  most  recent  improvements 

in  the  disintegration,   amalgamation,   smelting,   and  parting  of  the 

Precious  Ores,  with  a  Comprehensive  Digest  of  the  Mining  Laws. 

Greatly  augmented,  revised,  and  corrected.     By  JULIUS  SILVERSMITH. 

Fourth  edition.    Profusely  illustrated,     i  vol.,  i2mo.    Cloth.    $3. 

C  LOUGH.     The  Contractors'  Manual  and  Builders'  Price-Book.     By 
A.  B.  CLOUGH,  Architect,      i  vol.,  i8mo.     Cloth.     75  cents. 

BRUNNOW.      Spherical    Astronomy.     By   F.    BRTTNNOW,    Ph.    Dr. 
Translated  by  the  Author  from  the  Second  German  edition,      i 
vol.,  8vo.     Cloth.     $6.50. 

C~"HAUVENET  (Prof.  Wm.)     New  method  of  Correcting  Lunar  Dis- 
tances, and  Improved  Method  of  Finding  the  Error  and  Rate  of  a 
Chronometer,   by  equal  altitudes.     By  WM.  CHAUVENET,  LL.D.      i 
vol.,  8vo.     Cloth.     $2. 

A   SYNOPSIS   OF   BRITISH   GAS   LIGHTING,    comprising  the 
essence  of  the  "  London  Journal  of  Gas  Lighting"  from  1849  to 
1868.     Arranged  and  executed  by  JAMES  R.  SMEDBERG,  C.  E.  of  the 
San  Francisco  Gas  Works.     Issued  only  to  subscribers.     4to.    Cloth. 
$15.00     In  press. 

AS  WORKS  OF  LONDON.    By  ZERAH  COLBURN.    i2mo.    Boards. 
60  cents. 

HEWSON.     Principles    and    Practice   of   Embanking   Lands   from 
River  Floods,  as  applied  to  the  Levees  of  the  Mississippi.     By 
WILLIAM  HEWSON,  Civil  Engineer,      i  vol.,  8vo.     Cloth.     $2. 

"  This  is  a  valuable  treatise  on  the  principles  and  practice  of  embanking  lands  from  river 
Jloods,  as  applied  to  Levees  of  the  Mississippi,  by  a  highly  intelligent  and  experienced  engineer. 
The  author  says  it  is  a  first  attempt  to  reduce  to  order  and  to  rule  the  design,  execution,  and 
measurement  of  the  Levees  of  the  Mississippi.  It  is  a  most  use.lu!  and  need»v.  contribution  ta 
•ientific  literature."— Philadelphia  Evening  Journal. 


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Scientific  Books.  29 

WEISBACH  (Julius).     Principles  of  the  Mechanics  of  Machinery 
and   Engineering.     By   DR.    JULIUS   WEISBACH,    of  Freiburg. 
Translated  from  the  last  German  edition.     Vol.  i.  Svo,  cloth.     $10. 

HUNT  (R.  M.)    Designs  for  the  Gateways  of  the  Southern  Entrances 
to  the  Central  Park.     By  RICHARD  M.  HUNT.     With  a  descrip- 
tion of  the  designs,      i  vol.,  4to.     Illustrated.     Cloth.     $5. 

TDEET.     Manual  of  Inorganic  Chemistry  for  Students.     By  the  late 
-L        DUDLEY  PEET,  M.  D.    Revised  and  enlarged  by  ISAAC  LEWIS  PEET, 
A.  M.      i8mo.     Cloth.     75  cents. 

WHITNEY  (J.  P.)  Colorado,  in  the  United  States  of  America. 
Schedule  of  Ores  contributed  by  sundry  persons  to  the  Paris 
Universal  Exposition  of  1867,  with  some  Information  about  the 
Region  and  its  Resources.  By  J.  P.  WHITNEY,  of  Boston,  Com- 
missioner from  the  Territory.  Pamphlet.  8vo.,  with  maps.  Lon- 
don, 1867.  25  cents. 

WHITNEY  (J.  P.)     Silver  Mining  Regions  of  Colorado,  with  some 
account  of  the  different  processes  now  being  introduced  for 
working   the   Gold   Ores   of  that   Territory.     By  J.    P.    WHITNEY. 
I2mo.     Paper.     25  cents. 

"  This  is  a  most  valuable  little  book,  containing  a  vast  amount  of  practical  information  about 
that  region.  It  will  be  found  useful  to  men  of  a  scientific  turn  of  mind,  should  they  never  COH- 
template  a  journey  to  the  region  of  silver  and  gold/' — fall  E'w&r  News. 

CILVER   DISTRICTS   OF   NEVADA.      8vo.,   with   map.     Paper. 
^     35  cents. 

McCORMICK  (R.  C.)      Arizona  :    Its    Resources   and    Prospects. 
By  Hon.  R.  C.  McCoRMiCK.    With  map.    Svo.    Paper.    25  cents. 

PETERS.     Notes  on  the  Origin,  Nature,  Prevention,  and  Treatment 
of  Asiatic  Cholera.     By  JOHN  C.  PETERS,  M.  D.     Second  edition. 
With  an  appendix  and  map.     iamo.     Cloth.     $1.50. 

SEYMOUR.     Western   Incidents  connected  with  the  Union  Pacific 
Railroad.     By  SILAS  SEYMOUR.      I2mo.     Cloth.     $i. 

EULOGIES  IN  MEMORY  OF  MAJ.-GEN.  JAMES  S.  WADS- 
WORTH  AND  COL.   PETER  A.  PORTER,  before  the  "  Cen- 
tury Association."     Tinted  paper.     Svo.     Paper.     $i. 

PALMER.     Antarctic  Mariners'  Song.     By  JAMES  CROXALL  PALMER, 
U.  S.  N.     Illustrated.     Cloth,  gilt,  bevelled  boards.     $3. 

"  The  poem  is  founded  upon  and  narrates  the  episodes  of  the  exploring  expedition  of  a  small 
jailing  vessel,  the  '  Flying  Fish,'  in  company  with  the  '  Peacock,'  in  the  South  Seas,  in  1S3&- 
42.  The  'Flying  Fish'  was  too  small  to  be  safe  or  comfortable  in  that  Antarctic  region,  al- 
though wo  find  in  the  poem  bnt  little  of  complaint  or  murmuring  at  the  hardships  the  sailors 
were  compelled  to  endure." — Athenaeum. 

FRENCH'S   ETHICS.     Practical  Ethics.     By  Rev.  J.  W.   FREXCH. 
D.  D.,  Professor  of  Ethics,  U.  S.  Military  Academy.     Prepared  foi 
the  Uf.e  of  Students  in  the  Military  Academy,     i  vol.     Svo.     Cloth, 

$4.53, 


Scientific   Books.  31 

THE  MECHANIC'S  AND  STUDENT'S  GUIDE  in  the  Designing 
and  Construction  of  General  Machine  Gearing,  as  Eccentrics, 
Screws,  Toothed  Wheels,  etc.,  and  the  Drawing  of  Rectilineal  and 
Curved  Surfaces ;  with  Practical  Rules  and  Details.  Edited  by 
FRANCIS  HERBERT  JOYNSON.  Illustrated  with  18  folded  plates.  8vo. 
Cloth.  $2.00. 

"The  aim  of  this  work  is  to  be  a  guide  to  mechanics  in  the  designing  and  construction 
of  general  machine-gearing.  This  design  it  well  fulfils,  being  plainly  and  sensibly  written,  and 
profusely  illustrated." — Sunday  Times. 

FREE-HAND   DRAWING  -    a  Guide  to  Ornamental,   Figure,  and 
Landscape    Drawing.       By    an    Art    Student.       i8mo.       Cloth. 
75  cents. 

THE  EARTH'S  CRUST  :  a  Handy  Outline  of  Geology.     By  DAVID 
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arrangement,  and  clear  and  easy,  and,  at  the  same  time,  forcible  in  style.  It  will  lead,  we  hope, 
to  the  introduction  of  Geology  into  many  schools  that  have  neither  time  nor  room  for  the  study 
of  large  treatises." — The  Aluseum. 

HISTORY    AND    PROGRESS    OF   THE    ELECTRIC    TELE- 
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TRON   TRUSS   BRIDGES  FOR   RAILROADS.      The  Method  of 

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USEFUL  INFORMATION  FOR   RAILWAY  MEN.      Compiled 
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REPORT  ON  MACHINERY  AND   PROCESSES  OF  THE  IN- 
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WORKS  ON  ELECTRICITY 

AND 

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By-    R.     S.     CULLEY, 

Engineer  to  the  Electric  and  Intel-national  Telegraph  Company. 

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HiSTORI  AND  PROGRESS  OF  THE  ELECTRIC  TELEGRAPH, 

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By    ROBERT    SABINE. 
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Modern  Practice  of  the  Electric  Telegraph. 

A  HAND-BOOK  FOR  ELECTRICIANS  AND  OPERATORS. 
By    FRANK    L.    POPE. 

lition.     8vo,  illustrated.     Cloth, 


THE    TELEGRAPH    MANUAL. 

A   COMPLETE   HISTORY   AND    DESCRIPTION    OF   THE 

SEMAPHORIC,    ELECTRIC,    AND    MAGNETIC    TELEGRAPHS 

OF 
EUROPE,   ASIA,   AFRICA,    AlfD    AMERICA, 

ANCIENT     AND     MODERN. 

WITH  SIX  HUNDRED  AND  TWENTY-FIVE  ILLUSTRATIONS. 
By    TAL.    P.    SHAFFNEK. 

8vo,  cloth,  $6.50. 


D.  VAST   ^OSTEA]\TD, 

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*,*  Any  of  the  above  sent  free  by  mail  on  receipt  of  price. 


CHARLES  T.  &  J.  IV.  CHESTER, 

104  Centre  St.,  New  York* 

ENGINEERS, 

AND    MANUFACTURERS    OF 

Instruments,  Batteries, 

AND    EVERY    DESCRIPTION    OF 


INSULATED  AND  OFFICE  WIKES. 

We  are  now  prepared  to  furnish,  after  an  experience  of  three  year?,  an  Insulated 
AViiv,  which  can  be  buried  in  the  earth  or  exposed  to  rain  and  sun,  or  to  the  vapor  of 
acids,  without  injury.  Professor  SII.LIMAN,  who  has  exposed  it  to  the  most  destructive 
agencies,  finds  that  it  remains  uninjured  in  an  atmosphere  of  ozone  which  would  de- 
stroy gutta-percha  in  a  few  hours.  It  exceeds  glass,  or  any  other  known  substance, 
as  a'non-conductor.  We  have  made  special  arrangements  to  furnish  this  article  for 
office  purposes  at  a  reduced  rate.  Also,  Agents  for  the  new  insulator, 

KRYOLITE. 

Haider  than  glass,  and  possessing  the  best  insulating  properties.   'We  construct  the 

DIFFERENTIAL  GALVANOMETERS  AND  RESISTANCE  BOXES 

used  bv  English  electricians,  and  described  in  this  work,  for  measuring  resistances  and 
ascertaining  faults. 

To  accommodate  these  instruments  to  the  wants  of  our  Telegraph  patrons  we  have 
made  them  at  different  prices,  as  the  absolute  accuracy  required  in  the  philosophical 
investigation  of  Electrical  phenomena  is  not  necessary  for  ordinary  telegraphic  prob- 
lems. These  instruments  instantly  determine  the  resistances  of  magnets  and  lines, 
and  furnish  every  required  assistance  in  line  tests. 

We  have  submitted  to  the  test  of  more  than  a  year's  active  use  our  new 

ENDURING     BATTERY. 

For  thirteen  months  it  has  given  a  constant  current,  day  and  night,  on  a  short  tele- 
graph line.  So  equal  is  the  current  derived  from  it  that  the  adjustments  of  magnets 
formerly  necessary  on  that  line  have  been  almost  entirely  dispensed  with.  The  con- 
sumption of  material  for  currents  equal  to  those  from  the  sulphate  of  copper  battery 
used  on  lines  from  the  same  office,  is  only  about  one-tenth.  The  reason  for  this  great 
difference  is  that  the  salts  decomposed  in  exciting  electrical  action  are  separate  from 
the  other  elements,  and  are  retained  in  a  reservoir  insulated,  but  allowed  to  escape  and 
carry  on  their  action  entirely  under  control.  Thus,  for  Electrical  Clocks,  where  the 
amount  of  current  required  is  very  small,  the  adjustments  can  be  so  made  that  the 
battery  will  last  two  years.  For  a  local,  this  battery  acts  admirably  ;  though  having 
less  quantity  force  than  many  now  in  use,  it  has  quite  power  enough  for  a  well  con- 
structed Sounder  or  Eegister. 
We  also  construct  a 


made  with  great  perfection.     It  is  very  compact,  works  on  one  wire,  does  not  easily 
get  out  of  order,  works  with  speed,  and  will,  in  many  cases,  be  used  for  commercial 
purposes  on  private  lines  where  our  dial  instruments  have  been  largely  used. 
We  have,  after  a  test  of  live  years,  an 

ALPHABETICAL     TELEGRAPH 

in  extensive  use.     Over  thirty  of  these  are  employed  in  the  Police  Telegraph  System 
of  St.  Louis,  and  have  given  perfect  satisfaction.     They  are  used  by  the  Steamship 
Companies,  by  Iron  Founders,  Lumber  Merchants,  Coal  Dealers,  Sugar  Kctineries,  and 
wherever  the  nature  of  the  business  requires  a  separation  of  office  aiid  factory. 
We  supply  every  description  of 

ELECTRICAL    BE&CHINERV-  AND    APPLIANCES 

for  submarine  and  subterranean  blasting.     Also,  complete 

PORTABLE     APPARATUS 

For  the  safe  manufacture  of  NITROGLYCERINE  at  the  place  where  it  is  to  be  used. 
Our  Catalogue,  embracing  a  large  amount  of  new  matter  and  description,  is  now 
ready  for  distribution. 


CHESTER,  PARTRICK  &  CO, 


CONTRACTORS,  etc., 
37  South  Fourth  Street,  Philadelphia, 

Manufacturers  of  and  Dealers  in  every  variety  of 

TELEGRAPHIC,  ELECTRIC  AND  PHILOSOPHICAL  APPARATUS,  BAT- 

TERIES, WIRE,  ACIDS,  INSULATORS,  MEDICAL  INSTRUMENTS 

AND  OTHER  SUPPLIES. 

Also,  Contractors  for  the  construction,  re-construction  and  repair  of 

TELEGRAPH  LINES,    SIMPLE    BURGLAR  ALARMS  FOR  PRIVATE 

RESIDENCES,  AND  BURGLAR  ALARMS  WITH  "  TELL-TALE 

CLOCK,"  AND  OTHER  APPARATUS   FOR  BANKS 

AND  PUBLIC  BUILDINGS. 

Among  other  Telegraphic  Supplies  constantly  kept  on  hand,  they  are  prepared 
to  furnish  promptly  the  following  novel  articles  : 

KERITE  (OR  HORN  COVERED)  COPPER,   OR  COMPOUND  WIRE  OR 

CABLES, 

COVERED  COMPOUND  AIR  LINE  WIRE  ; 

BLASTING  APPARATUS,  CARTRIDGES,  BATTERIES,  &c.,  &c. 
CALCIUM  LIGHTING  APPARATUS, 

MEDICAL  BATTERIES, 

INDUCED  AND  DIRECT  CURRENTS  ; 

ELECTRO-PLATERS'  BATTERIES  AND  MATERIALS, 

ELECTRO  GONGS  OF  ANY  DESIRED  SIZE  OR  WEIGHT  ; 

ALARM  APPARATUS, 

PATENT  APPARATUS  for  the  MANUFACTURE  of  NITRO-GLYCERINE, 

ELECTRICAL  CLOCK-WORK, 

&c.,  &c.,  &c. 

They  guarantee  to  give  satisfact'.on  to  all  who  favor  them  with  orders,  in  the 
promptness  of  execution  and  in  the  quality  of  articles  supplied. 


L.  G.  TILLOTSON  &  CO., 

3STo.  :Q   T^e-y   Street,   3STev^  Y 

MANUFACTURERS  OF 

TELEGRAPH  INSTRUMENTS, 

BATTERIES    AND    SUPPLIES, 


OF    EVERY    DESCRIPTION, 


Glass  Insulators,  Plain  or  with  Screw;  Brackets,  &c.;  Zincs,  Tum- 
blers, Porous  Cups,  and  all  kinds  of  Battery  Material;  Hill's 
Patent  Galvanic  Battery ;  Ogden's  Improved  Carbons, 
with  the  Immersed  Platina  Connection;  Pure 
Nitric    and    Sulphuric    Acids;     Agents 
for  the  Best  English  and  American 
Plain  and  Galvanized  Wire. 

Agents  for  Gutta-Percha  Covered  Wire 

and  Cables,  American  Manufacture; 

Agents  of  American  Compound 

Telegraph   Wire   Company; 

SOLE    AGENTS    FOR 

Brooks'  Patent  Paraffine  Insulator. 

This  Insulator,  as  now  constructed,  is,  beyond  question,  the  best  in  use. 
MANUFACTURERS     OF 

JONES'   PATENT   LOCK   SWITCH    BOARD. 

e  invite  attention  to  our  cuts,  opposite  pages  29  and  35  of  this  work. 


BLISS,  TILLOTSON  &  CO,,  171  So,  Clark  St.,  Chicago, 


CHARLES  WILLIAMS,  JR., 

1O9   COURT    STREET, 

BOSTON,    MA.SS., 

(ESTABLISHED  1856.) 


MANUFACTURER    OF 


TELEGRAPH     INSTRUMENTS, 
BATTERIES  AISS  MATERIALS, 


'SOLK  MANUFACTURE  OF 

THE  GRIGim  CELEBRATED 

EMI-  A. 


All  Instruments  and  Materials  used  in  furnishing  and  working 

TELEGRAPH    LINES, 

• 

including  Registers,  Belays,  Main  Sounders,  Local  Sounders, 
Keys,  Switches,  Cut-outs,  Galvanometers,  Repeaters,  Arresters, 
Rheostats,  Resistance  Coils,  Boll  Calls,  Dial  Telegraphs,  Gongs, 
Batteries,  Porous  Cups,  Zincs,  Coppers,  Blue  Vitriol,  Acid,  Insu- 
lators, Line  Wire,  Insulated  Wire,  Cables,  etc.,  constantly  on 
hand,  and  for  sale  at  the  lowest  prices.  Also,  Electro-Medical 
Instruments  and  Magnetical  Apparatus  of  every  description. 


IMPROVED  PREMIUM  TELEGRAPH  INSTRUMENTS. 
DR.    L.    BRADLEY, 

Ko.  7  EXCHANGE  PLACE,  JERSEY  CITY,  N.  J. 

KEEPS  CONSTANTLY  ON  HAND  AND  FOR  SALE  HIS  CELEI  RATED 

flnjnmim  JmpromI  S^Irgraplt 


BRADLEY'S  Relays  were  awarded  the 

FIRST 


of  the  late  Great  Fair  of  the  American  Institute,  New  York,  and  their  superi- 
ority is  generally  acknowledged  by  operators  who  use  them. 

Aside  from  the  advantages  apparent  upon  inspection  of  these  magnets, 
their  acknowledged  merits  consist  in  the  construction  of  the  helix,  which  was 
patented  August  15,  1865  —  this  being  of  naked  copper  wire,  so  wound  that  the 
convolutions  are  separated  from  each  other  by  a  regular  and  uniform  space  of 
the  l-800th  of  an  inch,  the  layers  separated  by  thin  paper.  In  helices  of  silk 
insulated  wire  the  space  occupied  by  the  silk  is  the  l-150th  to  the  l-300th  of 
an  inch  ;  therefore  a  spool  made  of  a  given  length  and  size  of  naked  wire  will 
be  smaller,  and  will  contain  many  more  convolutions  around  the  core  than 
one  of  silk  insulated  wire,  and  will  make  a  proportionably  stronger  magnet, 
while  the  resistance  will  be  the  same. 

He  is  also  manufacturing  superior  Lightning  Arresters,  with  Cut-out 
Switch  and  Switches  for  grounding  either  wire. 

From  hundreds  of  testimonials  there  is  space  only  for  the  following  : 

80  BROADWAY,  NEW  YOEE,  March  15,  1870. 
L.  BRADLEY,  Esq. 

DEAR  SIB,  —  I  have  used  a  very  large  number  of  the  Magnets  manufactured 
by  you,  with  the  patent  naked  wire  helices,  principally  in  the  manufacture  of 
printing  instruments,  and  they  have  in  all  cases  given  entire  satisfaction. 
With  a  given  battery  power  and  equal  resistance,  I  have  found  them  20  per 
cent,  stronger  than  silk  covered  magnets  will  average.  They  are  remarkably 
even  in  quality  and  free  from  permanent  magnetism. 

FRANK  L.  POPF,  Electrical  Engineer. 

PRICKS 

will  be  as  favorable  as  goods  of  equal  or  approximate  excellence  can  be  pur- 
chased of  any  other  manufacturer. 

The  following  list  comprises  the  principal  articles  manufactured  and  sold 
at  this  establishment  : 

Button  Repeaters,  Pony  Sounders,  Keys. 

Kelays,  with  Helices  in  Bone  Rubber  Cylinders  (very  fine). 

Box  Relays,  large  and  small  ;  Excellent  Registers. 

Large  and  small  Box  Main  Sounders. 

A  new  style  of  both  Main  and  Local  Sounders  (very  loud  and  fine). 

Pocket  Relays,  with  all  the  adjustments  of  the  above,  and  good  Lever  Keys. 

All  other  kiuds  of  Telegraph  Apparatus  manufactured  to  order. 

Extra  Spools,  for  replacing  such  as  may  be  spoiled  by  lightning,  fur- 
nished at  $1.25  each.  Old  Spools  taken  at  the  price  of  new  wire  by  the  pound. 
Goods  sent  to  all  parts  of  the  continent  with  bill  C.  0.  D.  Or,  to  save  ex- 
pense of  returning  funds  by  express,  remittances  may  be  made  in  advance  by 
certified  check,  payable  in  New  York,  or  by  Post-office  order,  in  which  case 
he  will  make  no  charge  for  package. 

He  has  ample  facilities  for  furnishing  all  other  kinds  of  Telegraph  Sup- 
lisj  at  the  lowest  manufacturers'  prices. 


BROOKS' 

Patent  Paiaffine  Insulator  Works, 


;...::„':,..,  1  1 
21  Aspen  5>reet,  North  of  2123  Chestnut  Street,  Philadelphia,  Pa. 

DAVID  BROOKS,  Proprietor. 

L,  G,  TILLOTSON  &  CO,,  8  Dey  Street,  New  York, 


WORKS   ON   ELECTRICITY 

AND 

THE  ELECTEIC  TELEGEAPH, 

FOE   SALE   BY 

ID.     "V  ^  1ST     1ST  O  S  T  R^  1ST  D, 

PUBLISHER  AND  BOOKSELLER, 

23  Murray  Street   and  27  Warren  Sreent,  New  York. 

Prescott's  Theory  and  Practice  of  the   Electric  Telegraph.     12mr., 

illustrated.     Cloth,  $2.  50. 

Blight's  Electric   Telegraph.     12mo,  illustrated.     Cloth,  $1.75. 
Ferguson's   Electricity.     12mo,  illustrated.     Cloth,  $1.75. 
Noad's  Student's  Text-Book  of  Electricity.    Crown  8vo,  illust'd.    $6.25. 
Electrical  Measurement.  By  LATIMEK  CLABK.    12mo,  illustrated.   Cloth.  $3. 
The  Atlantic  Telegraph.     Its  History.     12mo,  illustrated.    Cloth,  $1.00. 
Blavier's  Traite  de  Telegraphic  Electrique.    2  vols.,  8vo.     Paper,  $10. 
Du  Moncel's  Traite  Theorique  et  Pratique  de  Telegraphic  Electrique. 

bvo.     Paper,  $5. 

Gavarret's  Telegraphic  Electrique.     12mo.     Paper,  $2.50. 
Tennant's    Manuel    Pratique    de    Telegraphic    Sous-Marine.      12mo. 

Paper,  SI.  75. 
Boussac  Precis  de  Telegraphic  Electrique.     8vo.     Paper,  $3.50. 


TZEiZE! 

JOURNAL  OF  THE  TELEGRAPH, 

A    SEMI-MONTHLY    PAPEK, 

DEVOTED    TO    THE 

Interests  of  the  Telegraph  in  the  United  States, 

And  a  record  of  its  progress  throughout  the  world. 

Published  on  the  1st  and  15th  of  each  Month, 

AT   THE 

EXECUTIVE   BOOMS  OF  THE  WESTEBN   UNION  TELEGRAPH  CO., 
145  BROADWAY.  NEW  YORK. 


The  JOUBNAL  OF  THE  TELEGKAPH  is  the  Official  Organ  of  the  Western 
Union  Telegraph  Company,  through  which  are  promulgated,  for  the  informa- 
tion of  the  Stockholders  and  the  public,  authentic  details  relating  to  tho 
financial  affairs  of  the  Company — embracing  a  monthly  statement  of  earn- 
ings, expenditures,  and  net  profits— and  the  orders  of  the  Executive  Offi- 
cers to  the  employes.  In  its  columns  will  also  be  found  accurate  and 
valuable  information  in  regard  to  the  operation  and  extension  of  the  lines, 
and  a  full  discussion  of  all  other  matters  of  a  scientific  or  general  character 
pertaining  to  the  telegraphic  art. 

Over  five  thousand  copies  of  the  JOURNAL  OF  THE  TELEGKAPH  are  now 
issued,  every  Telegraph  Office  in  the  country  receiving  one,  and  many  Stock- 
holders and  others  being  subscribers. 

TEKMS    OF    SUBSCEIPTION. 

One  copy,  one  year $1  00 

Five  copies,     "        400 

Single  copies,  five  cents. 


inserted  at  reasonable  rates.     All  communications  and  remittances  for  the 
JOURNAL  OF  THE  TELEGRAPH  should  be  addressed  to 

JAMES  D.  REID,  Editor, 

145  BRO  Jilt  WAY,  XJ2W  TO11K. 


THE '  TELEGRAPHER: 

A    JOURNAL    OF 

Electrical      I?  j?  ogress. 

PUBLISHED    EVERY    SATURDAY, 

AT 

Nos.  78  and  80  Broadway  (Room  48),  New  York. 

(OVER  THE  GOLD  EXCHANGE.) 
Devoted  strictly  and  exclusively  to  Telegraphic  interests,  and  the  only  recognized 

organ  of  the 

TELEGRAPHIC    PROFESSION 
in  this  country  or  the  world. 

Experience,  energy,  industry,  and  capital  will  all  be  combined  to  make  THE  TKI.F- 
GRAPHER  what  it  purports  to  be — A.  JOURNAL  OF  ELECTRICAL,  PROGRESS — and  to  rer- 
der  it  worthy  of  the  continuance  of  the  liberal  support  which  it  has  received  from  the 
profession  and  others  interested  in  E'ectrical  Science  and  Telegraphic  Art,  and  to  make 
it  a  creditable  representative  of  the  Practical  Telegraphic  Talent  of  the  United  State?. 
Correspondence,  items  of  news  or  personal  interest,  and  newspaper  extracts  relating 
to  Telegraphic  matters,  are  solicited.  The  co-operation  of  every  person  interested  in 
sustaining  a  first-class  Telegraphic  newspaper  is  cordially  invited. 

TERMS  OF  SUBSCRIPTION" : 

One  copy,  one  year $2  00 

Six  copies,  one  year  to  one  address  10  00 

Twelve"        "  ''         "       1700 

Single  copies,  five  cents. 

^^  Subscribers  in  the  British  Provinces  must  remit  20  cents,  Great  Britain, 
France,  Italy,  Spain  and  Portugal,  $1.04,  Russia,  Prussia,  and  the  west  coast  ot 
S^uth  America,  $3.12  per  annum,  in  addition  to  the  subscription  price,  for  prepay- 
ment of  American  postage. 

THE  PAPER  WILL  ALWAYS  BE  DISCONTINUED  WHEN  THE  PAID  SUBSCRIPTION  EX- 
PIRES. 

Remittances  may  be  made  by  Registered  Letter  or  Post-office  Order,  at  our  risk. 


will  be  inserted  at  reasonable  rates,  but  no  Advertisement  will  be  inserted  for  less  than 
One  Dollar  for  each  insertion. 

Any  persons  who  may  interest  themselves  in  procuring  Subscribers  at  the  adver- 
tised rates,  and  remitting  us  the  money,  will  be  entitled  to  an  extra  copy  for  one  year, 
for  every  club  of  not  less  than  six  Subscribers'. 

All  communications,  and  letters  relating  to  or  intended  for  THE  TELEGRAPHER, 
must  be  addressed  to  the 

PUBLISHER  AND  EDITOR, 

P,  O.   BOX  6010, 

NEW   YORK. 


m 

53(03 

n 


THE  LIBRARY 
UNIVERSITY  OF  CALIFORNIA 

Santa  Barbara 


•    THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW. 


A 


